Fair Value Measurements, Fair Value of Assets Measured on Recurring Basis, Unobservable Input Reconciliation (Details) - Mortgage Banking Derivatives, Net [Member] - Recurring [Member] - USD ($) $ in Thousands |
3 Months Ended | 12 Months Ended |
|---|---|---|
Mar. 31, 2018 |
Dec. 31, 2017 |
|
| Assets measured on recurring basis, unobservable input reconciliation [Roll Forward] | ||
| Beginning balance | $ 2,004 | $ 3,334 |
| Mortgage derivative gain, net | 977 | (1,330) |
| Ending balance | $ 2,981 | $ 2,004 |