Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Cash Flows from Operating Activities
Net income	$ 66,679	$ 63,816
Adjustments to reconcile net income to net cash provided by operating activities:
Reversal for credit losses		(3,000)
Provision for losses on other real estate owned	72	33
Deferred tax liability	4,333	3,597
Depreciation and amortization	1,626	2,009
Amortization of right-of-use asset	2,071
Change in operting lease liabilities	(1,802)
Net gains on sale and transfer of other real estate owned	19	(258)
Proceeds from sales of loans		8,000
Amortization on alternative energy partnerships, venture capital and other investments	10,812	(12)
Amortization/accretion of security premiums/discounts, net	439	882
Unrealized (gain)/loss on equity securities	(4,163)	3,847
Stock based compensation and stock issued to officers as compensation	1,534	1,499
Net change in accrued interest receivable and other assets	14,787	7,870
Gain on acquisition		(340)
Net change in other liabilities	(9,209)	(2,995)
Net cash provided by operating activities	87,198	84,948
Cash Flows from Investing Activities
Decrease in interest-bearing deposits		5,000
Purchase of investment securities available-for-sale	(154,924)	(125,714)
Proceeds from repayments, maturities and calls of investment securities available-for-sale	74,637	173,915
Purchase of Federal Home Loan Bank stock	(975)
Redemptions of Federal Home Loan Bank stock	975	5,835
Net increase in loans	(281,193)	(141,205)
Purchase of premises and equipment	(1,502)	(638)
Proceeds from sales of other real estate owned	61	1,480
Net increase in investment in affordable housing and alternative energy partnerships	(10,744)	(10,673)
Net cash used for investing activities	(373,665)	(92,000)
Cash Flows from Financing Activities
Net increase in deposits	383,883	322,166
Repayment of Federal Home Loan Bank borrowings	(2,020,000)	(1,255,000)
Cash dividends paid	(24,967)	(19,469)
Repayment of other borrowings	(15,000)
Purchases of treasury stock	(8,601)
Proceeds from shares issued under Dividend Reinvestment Plan	835	664
Proceeds from exercise of stock options		838
Taxes paid related to net share settlement of RSUs	(1,593)	(3,223)
Net cash provided by financing activities	224,557	195,976
(Decrease)/increase in cash, cash equivalents, and restricted cash	(61,910)	188,924
Cash, cash equivalents, and restricted cash, beginning of the period	600,290	534,801
Cash, cash equivalents, and restricted cash, end of the period	538,380	723,725
Supplemental disclosure of cash flow information
Interest	41,754	22,509
Income taxes paid	2,500	3,658
Non-cash investing and financing activities:
Net change in unrealized holding loss on securities available-for-sale, net of tax	8,799	(11,514)
Net change in unrealized holding loss on cash flow hedge derivatives	(1,224)	2,193
Transfers to other real estate owned from loans held for investment		715
Business Acquired During the Period [Member]
Cash Flows from Financing Activities
Advances from Federal Home Loan Bank	$ 1,910,000	$ 1,150,000