Quarterly Financial Information (Unaudited) - Quarterly Financial Information (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Quarterly Financial Information Disclosure [Abstract]
Interest and Dividend Income, Operating	$ 146,453	$ 142,615	$ 135,670	$ 119,546	$ 111,371	$ 104,497	$ 98,047	$ 86,617	$ 544,284	$ 400,532	$ 311,900
Total interest expense	104,237	97,557	91,737	76,317	70,088	64,935	58,316	49,546	369,848	242,885	171,626
Net interest income	42,216	45,058	43,933	43,229	41,283	39,562	39,731	37,071	174,436	157,647	140,274
Provision for loan losses	(146)	(99)	(424)	431	(474)	(270)	(327)	(637)	(238)	(1,708)	(1,065)
Interest Income (Expense), after Provision for Loan Loss	42,070	44,959	43,509	43,660	40,809	39,292	39,404	36,434	174,198	155,939	139,209
Guarantee and commitment fees	3,506	3,490	3,481	3,499	3,484	3,314	3,472	3,844	13,976	14,114	14,868
Gain (loss) on derivatives instruments and hedging activity net pretax	(2,999)	628	2,534	(3,850)	(1,777)	661	(617)	2,486
Gains/(losses) on trading securities	57	(3)	11	16	60	0	(2)	(82)	81	(24)	1,460
Gains on sale of available-for-sale investment securities					0	89	0	0	0	89	(9)
(Losses)/gains on sale of real estate owned	0	(41)	34	0	964	32	757	(5)	(7)	1,748	15
Other income	118	365	320	574	(58)	203	134	553	1,377	832	1,823
Noninterest Income	682	4,439	6,380	239	2,673	4,299	3,744	6,796	11,740	17,512	20,468
Noninterest Expense	13,703	11,650	12,921	11,642	10,210	10,616	11,390	10,549	49,916	42,765	40,320
Net income	29,049	37,748	36,968	32,257	33,272	32,975	31,758	32,681	136,022	130,686	119,357
Income tax expense	6,193	7,979	7,332	6,438	13,266	11,193	11,124	10,786	27,942	46,369	42,057
Net income	22,856	29,769	29,636	25,819	20,006	21,782	20,634	21,895	108,080	84,317	77,300
Less: Net loss attributable to non-controlling interest					0	0	150	15	0	165	34
Net Income (Loss) Attributable to Parent	22,856	29,769	29,636	25,819	20,006	21,782	20,784	21,910	108,080	84,482	77,334
Preferred Stock Dividends, Income Statement Impact	(3,296)	(3,295)	(3,296)	(3,295)	(3,296)	(3,295)	(3,296)	(3,295)	(13,182)	(13,182)	(13,182)
Net Income (Loss) Available to Common Stockholders, Basic	$ 19,560	$ 26,474	$ 26,340	$ 22,524	$ 16,710	$ 18,487	$ 17,488	$ 18,615	$ 94,898	$ 71,300	$ 64,152
Basic earnings per common share	$ 1.84	$ 2.48	$ 2.47	$ 2.12	$ 1.57	$ 1.74	$ 1.65	$ 1.76	$ 8.91	$ 6.73	$ 6.12
Diluted earnings per common share	$ 1.82	$ 2.46	$ 2.45	$ 2.10	$ 1.55	$ 1.71	$ 1.62	$ 1.73	$ 8.83000	$ 6.6000	$ 5.97000