Investment Securities and Fair Value Measurements - Sales, Calls and Maturities (Details) - USD ($)
$ in Thousands |
3 Months Ended |
Mar. 31, 2018 |
Mar. 31, 2017 |
| Schedule of Available-for-sale Securities [Line Items] |
|
|
| Gross Realized Gains |
$ 0
|
$ 0
|
| Gross Realized Losses |
0
|
0
|
| Gross Proceeds from Sales |
5
|
0
|
| Gross Proceeds from Maturities |
8,296
|
4,445
|
| Accretion (amortization) of discounts and premiums |
200
|
100
|
| Corporate bonds |
|
|
| Schedule of Available-for-sale Securities [Line Items] |
|
|
| Gross Realized Gains |
0
|
0
|
| Gross Realized Losses |
0
|
0
|
| Gross Proceeds from Sales |
0
|
0
|
| Gross Proceeds from Maturities |
6,300
|
3,200
|
| Agency securities |
|
|
| Schedule of Available-for-sale Securities [Line Items] |
|
|
| Gross Realized Gains |
0
|
|
| Gross Realized Losses |
0
|
|
| Gross Proceeds from Sales |
0
|
|
| Gross Proceeds from Maturities |
1,000
|
|
| Certificates of deposit |
|
|
| Schedule of Available-for-sale Securities [Line Items] |
|
|
| Gross Realized Gains |
0
|
0
|
| Gross Realized Losses |
0
|
0
|
| Gross Proceeds from Sales |
0
|
0
|
| Gross Proceeds from Maturities |
996
|
$ 1,245
|
| Treasury securities |
|
|
| Schedule of Available-for-sale Securities [Line Items] |
|
|
| Gross Realized Gains |
0
|
|
| Gross Realized Losses |
0
|
|
| Gross Proceeds from Sales |
5
|
|
| Gross Proceeds from Maturities |
$ 0
|
|