Acquisitions - Unaudited Pro Forma Combined Results of Operations (Details) - Standard Bancshares, Inc. - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Business Acquisition [Line Items]
Total revenues	[1]	$ 163,241	$ 164,786	$ 482,526	$ 462,962
Net income		$ 38,462	$ 32,589	$ 106,848	$ 85,054

[1] Includes net interest income and total noninterest income.