Goodwill and Core Deposit Intangibles - Schedule of Core Deposit Intangibles Activity (Details) - USD ($) $ in Thousands			12 Months Ended
	May 30, 2017	Aug. 12, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Finite-lived Intangible Assets [Roll Forward]
Current period amortization			$ 5,438	$ 3,427	$ 3,388
Core Deposits Intangibles
Finite-lived Intangible Assets [Roll Forward]
CDI, net, beginning of period			9,700	10,600	13,300
Established through acquisitions	$ 48,000	$ 2,500			700
Reductions due to sale of accounts			(3,200)	0	0
Current period amortization			5,400	3,400	3,400
Total CDI, net, at end of period			$ 49,100	$ 9,700	$ 10,600