Fair Value Measurements Notional Amount of Financial Instruments (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Notional Disclosures [Abstract]
Best efforts contracts and related committed IRLCs	$ 2,182	$ 6,607
Uncommitted IRLCs	50,746	66,875
FMBSs related to uncommitted IRLCs	53,000	66,000
Best efforts contracts and related mortgage loans held for sale	80,956	125,348
FMBSs related to mortgage loans held for sale	91,000	33,000
Mortgage loans held for sale covered by FMBSs	$ 90,781	$ 32,870