Goodwill and Other Intangible Assets - Summary (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Finite-Lived Intangible Assets [Line Items]
Intangible, net	$ 16,960	$ 23,806
Goodwill	307,112	220,591	$ 142,025
Total goodwill and other intangible assets, net	324,072	244,397
Core deposit intangible
Finite-Lived Intangible Assets [Line Items]
Intangible, gross	62,652	62,652
Less: accumulated amortization	(46,141)	(41,229)
Intangible, net	16,511	21,423
Noncompete agreement
Finite-Lived Intangible Assets [Line Items]
Intangible, gross	3,144	3,144
Less: accumulated amortization	(2,695)	(761)
Intangible, net	$ 449	$ 2,383