Fair Value Measurements Notional Amount of Financial Instruments (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Notional Disclosures [Abstract]
Whole loan contracts and related committed IRLCs	$ 8,163	$ 2,182
Uncommitted IRLCs	135,450	50,746
FMBSs related to uncommitted IRLCs	143,000	53,000
Whole loan contracts and related mortgage loans held for sale	11,015	80,956
FMBSs related to mortgage loans held for sale	103,000	91,000
Mortgage loans held for sale covered by FMBSs	$ 103,258	$ 90,781