Quarterly Results of Operations (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Summary of the unaudited quarterly results of operations
Interest income	$ 85,840	$ 83,032	$ 84,008	$ 76,259	$ 77,788	$ 74,300	$ 56,769	$ 54,166	$ 329,138	$ 263,023	$ 226,409
Interest expense	7,791	7,301	6,851	6,205	5,437	5,688	5,155	5,385	28,147	21,665	23,927
Net interest income	78,049	75,731	77,157	70,054	72,351	68,612	51,614	48,781	300,991	241,358	202,482
Provision for loan losses	1,650	2,650	1,430	1,800	1,750	750	1,175	1,075	7,530	4,750	6,167
Noninterest income	30,071	38,272	35,586	33,302	31,442	32,079	22,879	21,870	137,415	108,270	80,509
Noninterest expense	71,374	76,468	77,259	69,814	70,734	75,979	51,082	47,319	295,099	245,114	190,937
Income before income taxes	35,096	34,885	34,054	31,742	31,309	23,962	22,236	22,257	135,777	99,764	85,887
Income taxes	11,461	11,706	11,154	10,526	10,149	7,742	6,842	7,017	44,847	31,750	26,305
Net income	$ 23,635	$ 23,179	$ 22,900	$ 21,216	$ 21,160	$ 16,220	$ 15,394	$ 15,240	$ 90,930	$ 68,014	$ 59,582
Basic earnings per share (usd per share)	$ 0.56	$ 0.55	$ 0.54	$ 0.53	$ 0.53	$ 0.40	$ 0.49	$ 0.48	$ 2.18	$ 1.89	$ 1.89
Diluted earnings per share (usd per share)	$ 0.55	$ 0.55	$ 0.54	$ 0.52	$ 0.52	$ 0.40	$ 0.48	$ 0.48	$ 2.17	$ 1.88	$ 1.88