Goodwill and Other Intangible Assets - Summary of Finite-Lived Intangible Assets (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Finite-Lived Intangible Assets, Net [Abstract]
Gross Carrying Amount	$ 56,928	$ 56,928
Accumulated Amortization	(35,663)	(32,418)
Net Carrying Amount	21,265	24,510
Core Deposit Intangibles
Finite-Lived Intangible Assets, Net [Abstract]
Gross Carrying Amount	54,958	54,958
Accumulated Amortization	(34,765)	(31,586)
Net Carrying Amount	20,193	23,372
Customer Relationship Intangible
Finite-Lived Intangible Assets, Net [Abstract]
Gross Carrying Amount	1,970	1,970
Accumulated Amortization	(898)	(832)
Net Carrying Amount	$ 1,072	$ 1,138