Fair Value Measurements Notional Amount of Financial Instruments (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Notional Disclosures [Abstract]
Whole loan contracts and related committed IRLCs	$ 3,350	$ 2,182
Uncommitted IRLCs	109,800	50,746
FMBSs related to uncommitted IRLCs	110,000	53,000
Whole loan contracts and related mortgage loans held for sale	7,465	80,956
FMBSs related to mortgage loans held for sale	101,000	91,000
Mortgage loans held for sale covered by FMBSs	$ 101,171	$ 90,781