Quarterly Results of Operations (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Quarterly Financial Information Disclosure [Abstract]
Interest income	$ 90,348	$ 84,847	$ 71,467	$ 68,234	$ 65,005	$ 64,376	$ 62,704	$ 61,227	$ 314,896	$ 253,312	$ 221,198
Interest expense	11,583	10,427	8,367	7,235	6,631	6,694	6,742	6,772	37,612	26,839	24,794
NET INTEREST INCOME	78,765	74,420	63,100	60,999	58,374	57,682	55,962	54,455	277,284	226,473	196,404
Provision for loan losses	1,800	2,083	2,875	2,385	2,417	1,900	790	550	9,143	5,657	417
NET INTEREST INCOME AFTER PROVISION FOR LOAN LOSSES	76,965	72,337	60,225	58,614	55,957	55,782	55,172	53,905	268,141	220,816	195,987
Non-interest income	19,061	18,668	18,434	14,846	16,120	16,861	16,385	15,837	71,009	65,203	69,868
Non-interest expense	56,433	58,708	47,316	43,099	41,934	44,115	44,835	46,475	205,556	177,359	174,806
INCOME BEFORE INCOME TAX	39,593	32,297	31,343	30,361	30,143	28,528	26,722	23,267
Income tax expense	15,210	7,939	7,207	7,168	7,850	7,469	6,716	5,574	37,524	27,609	25,665
NET INCOME AVAILABLE TO COMMON STOCKHOLDERS	$ 24,383	$ 24,358	$ 24,136	$ 23,193	$ 22,293	$ 21,059	$ 20,006	$ 17,693	$ 96,070	$ 81,051	$ 65,384
Basic EPS (in dollars per share)	$ 0.49	$ 0.50	$ 0.57	$ 0.57	$ 0.55	$ 0.51	$ 0.50	$ 0.43	$ 2.13	$ 1.99	$ 1.73
Diluted EPS (in dollars per share)	$ 0.49	$ 0.50	$ 0.57	$ 0.56	$ 0.55	$ 0.51	$ 0.49	$ 0.43	$ 2.12	$ 1.98	$ 1.72
Average Shares Outstanding:
Basic (in shares)	49,144,310	48,431,880	42,038,824	40,984,481	40,846,650	40,779,423	40,751,720	40,690,573	45,181,221	40,767,343	37,816,399
Diluted (in shares)	49,379,303	48,643,774	42,243,539	41,220,586	41,124,179	41,025,784	40,969,111	40,916,972	45,402,978	41,013,133	38,088,233