Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($)	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Cash Flows from Operating Activities
Net income	$ 100,356,000	$ 80,994,000
Adjustments to reconcile net income to net cash provided by/(used in) operating activities:
Reversal for loan losses	(2,500,000)	(15,650,000)
Provision for losses on other real estate owned	483,000	383,000
Deferred tax liability	12,227,000	7,098,000
Depreciation and amortization	3,504,000	3,861,000
Net gains on sale and transfer of other real estate owned	(317,000)	(228,000)
Net gains on sale of loans		(201,000)
Proceeds from sales of loans	7,500,000	6,065,000
Originations of loans held-for-sale		(8,789,000)
Amortization on alternative energy partnerships, venture capital and other investments	1,682,000	25,264,000
Net loss/(gain) on sales and calls of securities	438,000	(1,655,000)
Amortization/accretion of security premiums/discounts, net	1,293,000	3,404,000
Write-down on impaired securities	25,000	206,000
Stock based compensation and stock issued to officers as compensation	3,107,000	2,623,000
Net change in accrued interest receivable and other assets	603,000	(4,690,000)
Net change in other liabilities	1,832,000	(7,212,000)
Net cash provided by operating activities	130,233,000	91,473,000
Cash Flows from Investing Activities
Decrease/(increase) in short-term investments	573,172,000	(170,047,000)
Purchase of investment securities available-for-sale	(349,550,000)	(290,901,000)
Proceeds from sale of investment securities available-for-sale	99,541,000	241,844,000
Proceeds from repayments, maturities and calls of investment securities available-for-sale	198,619,000	415,656,000
Net increase in loans	(369,751,000)	(350,810,000)
Purchase of premises and equipment	(1,718,000)	(1,857,000)
Proceeds from sales of other real estate owned	1,399,000	828,000
Net increase in investment in affordable housing and alternative energy partnerships	(16,685,000)	(47,420,000)
Net cash provided by (used for) investing activities	135,027,000	(202,707,000)
Cash Flows from Financing Activities
Net decrease in deposits	(211,228,000)	(37,711,000)
Net decrease in federal funds purchased and securities sold under agreements to repurchase	(200,000,000)
Advances from Federal Home Loan Bank	795,000,000	1,755,000,000
Repayment of Federal Home Loan Bank borrowings	(670,000,000)	(1,475,000,000)
Cash dividends paid	(33,524,000)	(28,375,000)
Purchases of treasury stock		(54,441,000)
Proceeds from shares issued under Dividend Reinvestment Plan	1,233,000	1,096,000
Proceeds from exercise of stock options	877,000	49,000
Taxes paid related to net share settlement of RSUs	(5,118,000)	(103,000)
Net cash (used in) financing activities	(322,760,000)	160,515,000
(Decrease)/increase in cash and cash equivalents	(57,500,000)	49,281,000
Cash and cash equivalents, beginning of the period	218,017,000	180,130,000
Cash and cash equivalents, end of the period	160,517,000	229,411,000
Supplemental disclosure of cash flow information
Interest	39,259,000	40,740,000
Income taxes paid	30,096,000	30,698,000
Non-cash investing and financing activities:
Net change in unrealized holding gain on securities available-for-sale, net of tax	2,546,000	13,970,000
Net change in unrealized holding loss on cash flow hedge derivatives	(251,000)	(4,402,000)
Transfers to other real estate owned from loans held for investment	726,000	2,698,000
Loans transferred from held for sale to held for investment, net		$ 3,751,000