Business Combinations - Pro Forma Information (Details) - Integrity Bancshares, Inc. [Member] - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Business Acquisition, Pro Forma Information [Abstract]
Total revenue(1)	[1]	$ 60,307	$ 57,921	$ 118,992	$ 115,045
Net income	[2]	$ 18,816	$ 17,765	$ 32,728	$ 33,697
Earnings per common share:
Basic (in USD per share)	[2]	$ 0.54	$ 0.51	$ 0.95	$ 0.97
Diluted (in USD per share)	[2]	$ 0.54	$ 0.51	$ 0.94	$ 0.97

[1] Total pro forma revenue is defined as net interest income plus non-interest income, excluding gains and losses on sales of investment securities available-for-sale.

[2] Excludes merger expenses