Quarterly Results of Operations (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Quarterly Financial Information Disclosure [Abstract]
Interest income	$ 56,514	$ 56,538	$ 55,202	$ 52,944	$ 53,053	$ 53,290	$ 51,527	$ 51,009	$ 221,198	$ 208,879	$ 170,834
Interest expense	6,440	6,215	6,171	5,968	5,893	5,424	5,408	5,117	24,794	21,842	16,569
NET INTEREST INCOME	$ 50,074	$ 50,323	49,031	$ 46,976	47,160	47,866	$ 46,119	$ 45,892	196,404	187,037	154,265
Provision for loan losses			417		960	1,600			417	2,560	6,648
NET INTEREST INCOME AFTER PROVISION FOR LOAN LOSSES	$ 50,074	$ 50,323	48,614	$ 46,976	46,200	46,266	$ 46,119	$ 45,892	195,987	184,477	147,617
Non-interest income	14,767	16,899	24,633	16,232	16,375	18,412	16,179	15,434	72,531	66,400	56,016
Non-interest expense	46,246	43,598	46,423	41,202	41,677	42,576	41,250	43,089	177,469	168,592	143,219
INCOME BEFORE INCOME TAX	18,595	23,624	26,824	22,006	20,898	22,102	21,048	18,237	91,049	82,285	60,414
Income tax expense	4,418	6,557	8,856	5,834	5,638	5,980	5,888	4,617	25,665	22,123	15,884
NET INCOME	$ 14,177	$ 17,067	$ 17,968	$ 16,172	$ 15,260	$ 16,122	$ 15,160	$ 13,620	$ 65,384	$ 60,162	$ 44,530
Basic EPS (in dollars per share)	$ 0.37	$ 0.46	$ 0.47	$ 0.43	$ 0.41	$ 0.45	$ 0.42	$ 0.38	$ 1.73	$ 1.66	$ 1.42
Diluted EPS (in dollars per share)	$ 0.37	$ 0.45	$ 0.47	$ 0.43	$ 0.41	$ 0.45	$ 0.41	$ 0.38	$ 1.72	$ 1.65	$ 1.41
Average Shares Outstanding:
Basic (in shares)	37,908,873	37,850,827	37,793,448	37,709,883	37,018,014	36,054,867	36,026,763	35,956,436	37,816,399	36,266,356	29,731,420
Diluted (in shares)	38,190,694	38,118,199	38,043,359	38,000,074	37,323,276	36,328,981	36,294,149	36,260,624	38,088,233	36,554,609	30,008,380