Fair Value - Fair Value by Hierarchy (Details) - USD ($)
$ in Thousands |
Mar. 31, 2018 |
Dec. 31, 2017 |
| Fair Value, Assets and Liabilities Measured on Recurring Basis |
|
|
| Available-for-sale securities: |
$ 1,497,930
|
$ 1,539,653
|
| Recurring basis | Level 2 |
|
|
| Fair Value, Assets and Liabilities Measured on Recurring Basis |
|
|
| Long-term debt |
286,300
|
290,800
|
| Fair Value |
|
|
| Fair Value, Assets and Liabilities Measured on Recurring Basis |
|
|
| Cash and cash equivalents |
88,793
|
107,589
|
| Long-term debt |
286,330
|
290,824
|
| Fair Value | Fixed Maturities |
|
|
| Fair Value, Assets and Liabilities Measured on Recurring Basis |
|
|
| Available-for-sale securities: |
1,497,930
|
1,441,107
|
| Fair Value | Equity securities |
|
|
| Fair Value, Assets and Liabilities Measured on Recurring Basis |
|
|
| Available-for-sale securities: |
90,498
|
96,004
|
| Fair Value | Short-term investments |
|
|
| Fair Value, Assets and Liabilities Measured on Recurring Basis |
|
|
| Available-for-sale securities: |
0
|
2,541
|
| Fair Value | Recurring basis |
|
|
| Fair Value, Assets and Liabilities Measured on Recurring Basis |
|
|
| Cash and cash equivalents |
88,793
|
107,589
|
| Total cash and investments |
$ 1,677,221
|
$ 1,647,242
|
| Percentage of total cash and investments (percent) |
100.00%
|
100.00%
|
| Fair Value | Recurring basis | Fixed Maturities |
|
|
| Fair Value, Assets and Liabilities Measured on Recurring Basis |
|
|
| Available-for-sale securities: |
$ 1,497,930
|
$ 1,441,107
|
| Fair Value | Recurring basis | U.S. government |
|
|
| Fair Value, Assets and Liabilities Measured on Recurring Basis |
|
|
| Available-for-sale securities: |
124,757
|
60,528
|
| Fair Value | Recurring basis | State and Municipal |
|
|
| Fair Value, Assets and Liabilities Measured on Recurring Basis |
|
|
| Available-for-sale securities: |
296,814
|
494,211
|
| Fair Value | Recurring basis | Mortgage- Backed Securities |
|
|
| Fair Value, Assets and Liabilities Measured on Recurring Basis |
|
|
| Available-for-sale securities: |
427,068
|
381,561
|
| Fair Value | Recurring basis | Residential |
|
|
| Fair Value, Assets and Liabilities Measured on Recurring Basis |
|
|
| Available-for-sale securities: |
365,007
|
350,992
|
| Fair Value | Recurring basis | Commercial |
|
|
| Fair Value, Assets and Liabilities Measured on Recurring Basis |
|
|
| Available-for-sale securities: |
62,061
|
30,569
|
| Fair Value | Recurring basis | Asset-backed securities |
|
|
| Fair Value, Assets and Liabilities Measured on Recurring Basis |
|
|
| Available-for-sale securities: |
128,484
|
62,418
|
| Fair Value | Recurring basis | Corporates |
|
|
| Fair Value, Assets and Liabilities Measured on Recurring Basis |
|
|
| Available-for-sale securities: |
520,807
|
442,390
|
| Fair Value | Recurring basis | Equity securities |
|
|
| Fair Value, Assets and Liabilities Measured on Recurring Basis |
|
|
| Available-for-sale securities: |
90,498
|
96,004
|
| Fair Value | Recurring basis | Short-term investments |
|
|
| Fair Value, Assets and Liabilities Measured on Recurring Basis |
|
|
| Available-for-sale securities: |
0
|
2,541
|
| Fair Value | Recurring basis | Level 1 |
|
|
| Fair Value, Assets and Liabilities Measured on Recurring Basis |
|
|
| Cash and cash equivalents |
88,793
|
107,589
|
| Total cash and investments |
$ 304,048
|
$ 264,121
|
| Percentage of total cash and investments (percent) |
18.10%
|
16.00%
|
| Fair Value | Recurring basis | Level 1 | Fixed Maturities |
|
|
| Fair Value, Assets and Liabilities Measured on Recurring Basis |
|
|
| Available-for-sale securities: |
$ 124,757
|
$ 60,528
|
| Fair Value | Recurring basis | Level 1 | U.S. government |
|
|
| Fair Value, Assets and Liabilities Measured on Recurring Basis |
|
|
| Available-for-sale securities: |
124,757
|
60,528
|
| Fair Value | Recurring basis | Level 1 | State and Municipal |
|
|
| Fair Value, Assets and Liabilities Measured on Recurring Basis |
|
|
| Available-for-sale securities: |
0
|
0
|
| Fair Value | Recurring basis | Level 1 | Mortgage- Backed Securities |
|
|
| Fair Value, Assets and Liabilities Measured on Recurring Basis |
|
|
| Available-for-sale securities: |
0
|
0
|
| Fair Value | Recurring basis | Level 1 | Residential |
|
|
| Fair Value, Assets and Liabilities Measured on Recurring Basis |
|
|
| Available-for-sale securities: |
0
|
0
|
| Fair Value | Recurring basis | Level 1 | Commercial |
|
|
| Fair Value, Assets and Liabilities Measured on Recurring Basis |
|
|
| Available-for-sale securities: |
0
|
0
|
| Fair Value | Recurring basis | Level 1 | Asset-backed securities |
|
|
| Fair Value, Assets and Liabilities Measured on Recurring Basis |
|
|
| Available-for-sale securities: |
0
|
0
|
| Fair Value | Recurring basis | Level 1 | Corporates |
|
|
| Fair Value, Assets and Liabilities Measured on Recurring Basis |
|
|
| Available-for-sale securities: |
0
|
0
|
| Fair Value | Recurring basis | Level 1 | Equity securities |
|
|
| Fair Value, Assets and Liabilities Measured on Recurring Basis |
|
|
| Available-for-sale securities: |
90,498
|
96,004
|
| Fair Value | Recurring basis | Level 1 | Short-term investments |
|
|
| Fair Value, Assets and Liabilities Measured on Recurring Basis |
|
|
| Available-for-sale securities: |
0
|
0
|
| Fair Value | Recurring basis | Level 2 |
|
|
| Fair Value, Assets and Liabilities Measured on Recurring Basis |
|
|
| Cash and cash equivalents |
0
|
0
|
| Total cash and investments |
$ 1,351,794
|
$ 1,379,373
|
| Percentage of total cash and investments (percent) |
80.60%
|
83.70%
|
| Fair Value | Recurring basis | Level 2 | Fixed Maturities |
|
|
| Fair Value, Assets and Liabilities Measured on Recurring Basis |
|
|
| Available-for-sale securities: |
$ 1,351,794
|
$ 1,376,832
|
| Fair Value | Recurring basis | Level 2 | U.S. government |
|
|
| Fair Value, Assets and Liabilities Measured on Recurring Basis |
|
|
| Available-for-sale securities: |
0
|
0
|
| Fair Value | Recurring basis | Level 2 | State and Municipal |
|
|
| Fair Value, Assets and Liabilities Measured on Recurring Basis |
|
|
| Available-for-sale securities: |
296,048
|
490,724
|
| Fair Value | Recurring basis | Level 2 | Mortgage- Backed Securities |
|
|
| Fair Value, Assets and Liabilities Measured on Recurring Basis |
|
|
| Available-for-sale securities: |
424,211
|
381,561
|
| Fair Value | Recurring basis | Level 2 | Residential |
|
|
| Fair Value, Assets and Liabilities Measured on Recurring Basis |
|
|
| Available-for-sale securities: |
365,007
|
350,992
|
| Fair Value | Recurring basis | Level 2 | Commercial |
|
|
| Fair Value, Assets and Liabilities Measured on Recurring Basis |
|
|
| Available-for-sale securities: |
59,204
|
30,569
|
| Fair Value | Recurring basis | Level 2 | Asset-backed securities |
|
|
| Fair Value, Assets and Liabilities Measured on Recurring Basis |
|
|
| Available-for-sale securities: |
110,836
|
62,266
|
| Fair Value | Recurring basis | Level 2 | Corporates |
|
|
| Fair Value, Assets and Liabilities Measured on Recurring Basis |
|
|
| Available-for-sale securities: |
520,698
|
442,281
|
| Fair Value | Recurring basis | Level 2 | Equity securities |
|
|
| Fair Value, Assets and Liabilities Measured on Recurring Basis |
|
|
| Available-for-sale securities: |
0
|
0
|
| Fair Value | Recurring basis | Level 2 | Short-term investments |
|
|
| Fair Value, Assets and Liabilities Measured on Recurring Basis |
|
|
| Available-for-sale securities: |
0
|
2,541
|
| Fair Value | Recurring basis | Level 3 |
|
|
| Fair Value, Assets and Liabilities Measured on Recurring Basis |
|
|
| Cash and cash equivalents |
0
|
0
|
| Total cash and investments |
$ 21,379
|
$ 3,748
|
| Percentage of total cash and investments (percent) |
1.30%
|
0.20%
|
| Fair Value | Recurring basis | Level 3 | Fixed Maturities |
|
|
| Fair Value, Assets and Liabilities Measured on Recurring Basis |
|
|
| Available-for-sale securities: |
$ 21,379
|
$ 3,748
|
| Fair Value | Recurring basis | Level 3 | U.S. government |
|
|
| Fair Value, Assets and Liabilities Measured on Recurring Basis |
|
|
| Available-for-sale securities: |
0
|
0
|
| Fair Value | Recurring basis | Level 3 | State and Municipal |
|
|
| Fair Value, Assets and Liabilities Measured on Recurring Basis |
|
|
| Available-for-sale securities: |
766
|
3,488
|
| Fair Value | Recurring basis | Level 3 | Mortgage- Backed Securities |
|
|
| Fair Value, Assets and Liabilities Measured on Recurring Basis |
|
|
| Available-for-sale securities: |
2,857
|
0
|
| Fair Value | Recurring basis | Level 3 | Residential |
|
|
| Fair Value, Assets and Liabilities Measured on Recurring Basis |
|
|
| Available-for-sale securities: |
0
|
0
|
| Fair Value | Recurring basis | Level 3 | Commercial |
|
|
| Fair Value, Assets and Liabilities Measured on Recurring Basis |
|
|
| Available-for-sale securities: |
2,857
|
0
|
| Fair Value | Recurring basis | Level 3 | Asset-backed securities |
|
|
| Fair Value, Assets and Liabilities Measured on Recurring Basis |
|
|
| Available-for-sale securities: |
17,647
|
152
|
| Fair Value | Recurring basis | Level 3 | Corporates |
|
|
| Fair Value, Assets and Liabilities Measured on Recurring Basis |
|
|
| Available-for-sale securities: |
109
|
108
|
| Fair Value | Recurring basis | Level 3 | Equity securities |
|
|
| Fair Value, Assets and Liabilities Measured on Recurring Basis |
|
|
| Available-for-sale securities: |
0
|
0
|
| Fair Value | Recurring basis | Level 3 | Short-term investments |
|
|
| Fair Value, Assets and Liabilities Measured on Recurring Basis |
|
|
| Available-for-sale securities: |
$ 0
|
$ 0
|