Consolidated Statements of Operations and Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
INTEREST AND DIVIDEND INCOME
Loan receivable	$ 549,291	$ 473,782	$ 427,621
Investment securities	20,531	21,426	21,523
Federal Home Loan Bank stock	1,798	2,099	3,164
Federal funds sold and securities purchased under agreement to resell	110
Deposits with banks	4,421	1,763	1,398
Total interest and dividend income	576,151	499,070	453,706
INTEREST EXPENSE
Time deposits	46,768	43,327	39,443
Other deposits	19,076	16,094	12,445
Interest on securities sold under agreements to repurchase	4,250	15,329	15,813
Advances from the Federal Home Loan Bank	2,712	659	487
Long-term debt	5,775	5,791	5,776
Deferred payments from acquisition	1,861
Total interest expense	80,442	81,200	73,964
Net interest income before reversal for credit losses	495,709	417,870	379,742
Reversal for credit losses	(2,500)	(15,650)	(11,400)
Net interest income after reversal for credit losses	498,209	433,520	391,142
NON-INTEREST INCOME
Securities gains/(losses), net	1,006	4,898	(3,349)
Letters of credit commissions	4,860	4,939	5,545
Depository service fees	5,624	5,478	5,348
Gain from acquisition	5,628
Other operating income	19,179	18,055	25,130
Total non-interest income	36,297	33,370	32,674
NON-INTEREST EXPENSE
Salaries and employee benefits	109,458	97,348	89,960
Occupancy expense	20,429	18,315	17,018
Computer and equipment expense	10,846	9,777	9,828
Professional services expense	20,439	18,686	17,316
Data processing service expense	11,190	8,957	7,698
FDIC and State assessments	10,633	9,712	9,087
Marketing expense	6,200	5,092	4,926
Other real estate owned income/(loss)	(1,649)	856	(800)
Operations of investments in affordable housing and alternative energy partnerships, net	27,212	40,264	33,335
Amortization of core deposit premium	930	689	667
Acquisition and integration costs	4,121
Other operating expense	16,390	14,994	13,685
Total non-interest expense	236,199	224,690	202,720
Income before income tax expense	298,307	242,200	221,096
Income tax benefit	122,265	67,101	59,987
Net income attributable to common stockholders	176,042	175,099	161,109
Other comprehensive income/(loss), net of tax:
Unrealized holding gains/(losses) on securities available for sale	1,068	6,725	(4,200)
Unrealized holding gains/(losses) on cash flow hedge derivatives	719	825	(598)
Less: reclassification adjustment for gains/(losses) included in net income	583	2,839	(1,941)
Total other comprehensive income/(loss), net of tax	1,204	4,711	(2,857)
Total comprehensive income	$ 177,246	$ 179,810	$ 158,252
Net income attributable to common stockholders per common share
Basic (in dollars per share)	$ 2.19	$ 2.21	$ 2
Diluted (in dollars per share)	$ 2.17	$ 2.19	$ 1.98
Basic average common shares outstanding (in shares)	80,262,782	79,153,762	80,563,577
Diluted average common shares outstanding (in shares)	81,004,550	79,929,262	81,294,796