Investments - Change in unrealized gains and losses (Details) - USD ($)
$ in Thousands |
3 Months Ended |
Mar. 31, 2018 |
Mar. 31, 2017 |
| Schedule of Available-for-sale Securities [Line Items] |
|
|
| Unrealized holding gains (losses) on securities arising during the period, pre-tax |
$ (18,344)
|
$ 10,664
|
| Unrealized holding gains (losses) on securities arising during the period, tax effects |
3,852
|
(3,733)
|
| Unrealized holding gains (losses) on securities arising during period, net of tax |
(14,492)
|
6,932
|
| Realized gains on securities sold, pre-tax |
(1,363)
|
(519)
|
| Realized gains on securities sold, tax effects |
(109)
|
182
|
| Realized gains on securities sold, net of tax |
409
|
(337)
|
| Net impairment losses recognized in earnings |
(1,588)
|
(10)
|
| Impairment loss recognized in earnings, tax effects |
(334)
|
(3)
|
| Impairment loss recognized in earnings |
1,255
|
6
|
| Other Comprehensive Income (Loss), Available-for-sale Securities, Tax |
(3,410)
|
3,554
|
| Change in unrealized gains (losses) on marketable securities, net, net of tax |
(12,828)
|
6,601
|
| Fixed Maturities |
|
|
| Schedule of Available-for-sale Securities [Line Items] |
|
|
| Unrealized holding gains (losses) on securities arising during the period, pre-tax |
(18,346)
|
4,368
|
| Realized gains on securities sold, pre-tax |
(519)
|
(52)
|
| Net impairment losses recognized in earnings |
1,588
|
10
|
| Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, before Tax |
(16,238)
|
4,429
|
| Equity securities |
|
|
| Schedule of Available-for-sale Securities [Line Items] |
|
|
| Unrealized holding gains (losses) on securities arising during the period, pre-tax |
|
6,294
|
| Realized gains on securities sold, pre-tax |
|
569
|
| Net impairment losses recognized in earnings |
|
0
|
| Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, before Tax |
|
5,725
|
| Short-term investments |
|
|
| Schedule of Available-for-sale Securities [Line Items] |
|
|
| Unrealized holding gains (losses) on securities arising during the period, pre-tax |
1
|
3
|
| Realized gains on securities sold, pre-tax |
1
|
1
|
| Net impairment losses recognized in earnings |
0
|
0
|
| Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, before Tax |
$ 0
|
$ 1
|