Quarterly Financial Information (Unaudited) - Quarterly Financial Information (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 and Dividend Income, Operating	$ 111,371	$ 104,497	$ 98,047	$ 86,617	$ 81,241	$ 79,532	$ 77,236	$ 73,891	$ 400,532	$ 311,900	$ 264,823
Total interest expense	70,088	64,935	58,316	49,546	44,528	43,969	42,878	40,251	242,885	171,626	139,016
Net interest income	41,283	39,562	39,731	37,071	36,713	35,563	34,358	33,640	157,647	140,274	125,807
Provision for loan losses	(474)	(270)	(327)	(637)	(461)	(191)	(364)	(49)	(1,708)	(1,065)	(2,388)
Interest Income (Expense), after Provision for Loan Loss	40,809	39,292	39,404	36,434	36,252	35,372	33,994	33,591	155,939	139,209	123,419
Guarantee and commitment fees	3,484	3,314	3,472	3,844	3,789	3,798	3,655	3,626	14,114	14,868	14,077
Gain (loss) on derivatives instruments and hedging activity net pretax	(1,777)	661	(617)	2,486	15,390	(1,601)	(4,696)	(6,782)
(Losses)/gains on trading securities	60	0	(2)	(82)	(474)	1,182	394	358	(24)	1,460	1,220
Gains/(losses) on sale of available-for-sale investment securities	0	89	0	0	0	0	0	(9)	89	(9)	9
Gains/(losses) on sale of real estate owned	964	32	757	(5)	0	15	0	0	1,748	15	(1)
Other income	(58)	203	134	553	602	707	413	101	832	1,823	2,305
Noninterest Income	2,673	4,299	3,744	6,796	19,307	4,101	(234)	(2,706)	17,512	20,468	20,141
Noninterest Expense	10,210	10,616	11,390	10,549	10,977	9,303	10,074	9,966	42,765	40,320	35,482
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	33,272	32,975	31,758	32,681	44,582	30,170	23,686	20,919	130,686	119,357	108,078
Income tax expense	13,266	11,193	11,124	10,786	15,793	10,529	8,400	7,335	46,369	42,057	34,239
Net income	20,006	21,782	20,634	21,895	28,789	19,641	15,286	13,584	84,317	77,300	73,839
Less: Net loss/(income) attributable to non-controlling interest	0	0	150	15	(28)	18	16	28	165	34	(5,139)
Net Income (Loss) Attributable to Parent	20,006	21,782	20,784	21,910	28,761	19,659	15,302	13,612	84,482	77,334	68,700
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	$ 16,710	$ 18,487	$ 17,488	$ 18,615	$ 25,465	$ 16,364	$ 12,006	$ 10,317	$ 71,300	$ 64,152	$ 47,371
Basic earnings per common share	$ 1.57	$ 1.74	$ 1.65	$ 1.76	$ 2.42	$ 1.56	$ 1.15	$ 0.99	$ 6.73	$ 6.12	$ 4.33
Diluted earnings per common share	$ 1.55	$ 1.71	$ 1.62	$ 1.73	$ 2.38	$ 1.54	$ 1.13	$ 0.94	$ 6.6000	$ 5.97000	$ 4.19000