Quarterly Results of Operations (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Interest income	$ 125,821	$ 118,132	$ 112,639	$ 108,813	$ 108,653	$ 104,800	$ 100,871	$ 93,620	$ 465,405	$ 407,944	$ 314,896
Interest expense	28,237	29,200	27,361	23,947	20,769	18,314	16,300	13,704	108,745	69,087	37,612
NET INTEREST INCOME	97,584	88,932	85,278	84,866	87,884	86,486	84,571	79,916	356,660	338,857	277,284
Provision for loan losses	500	600	500	1,200	1,664	1,400	1,663	2,500	2,800	7,227	9,143
NET INTEREST INCOME AFTER PROVISION FOR LOAN LOSSES	97,084	88,332	84,778	83,666	86,220	85,086	82,908	77,416	353,860	331,630	268,141
Non-interest income	24,245	22,116	21,614	18,713	19,180	19,527	18,191	19,561	86,688	76,459	71,009
Non-interest expense	65,201	67,354	57,587	56,621	57,738	55,022	53,504	53,687	246,763	219,951	205,556
Income before income tax expense	56,128	43,094	48,805	45,758	47,662	49,591	47,595	43,290
Income tax expense	8,298	6,337	7,749	6,941	5,949	8,478	7,961	6,611	29,325	28,999	37,524
Net income available to common stockholders	$ 47,830	$ 36,757	$ 41,056	$ 38,817	$ 41,713	$ 41,113	$ 39,634	$ 36,679	$ 164,460	$ 159,139	$ 96,070
Basic EPS (in dollars per share)	$ 0.87	$ 0.71	$ 0.83	$ 0.79	$ 0.85	$ 0.83	$ 0.80	$ 0.75	$ 3.20	$ 3.23	$ 2.13
Diluted EPS (in dollars per share)	$ 0.87	$ 0.71	$ 0.83	$ 0.78	$ 0.85	$ 0.83	$ 0.80	$ 0.74	$ 3.19	$ 3.22	$ 2.12
Average Shares Outstanding:
Basic (in shares)	55,348,176	51,433,227	49,432,167	49,369,024	49,314,276	49,286,945	49,252,580	49,192,647	51,412,133	49,262,015	45,181,221
Diluted (in shares)	55,519,953	51,569,557	49,549,887	49,540,844	49,511,233	49,492,019	49,451,406	49,427,972	51,561,238	49,470,923	45,402,978