Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($)	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
Cash Flows from Operating Activities
Net income	$ 127,084,000	$ 119,663,000
Adjustments to reconcile net income to net cash provided by/(used in) operating activities:
Credit for loan losses	(15,650,000)	(8,400,000)
Provision for losses on other real estate owned	176,000	547,000
Deferred tax liability	22,483,000	14,327,000
Depreciation and amortization	5,684,000	5,745,000
Net gains on sale and transfer of other real estate owned	(476,000)	(2,006,000)
Net gains on sale of loans	(285,000)	(845,000)
Proceeds from sales of loans	13,525,000	28,507,000
Originations of loans held-for-sale	(12,665,000)	(26,689,000)
Amortization on alternative energy partnerships, venture capital and other investments	27,282,000	16,993,000
Net gain on sales and calls of securities	(3,347,000)	(506,000)
Amortization/accretion of security premiums/discounts, net	5,193,000	3,542,000
Loss on sales or disposal of fixed assets	19,000	138,000
Write-down on impaired securities	206,000	3,875,000
Excess tax short-fall from share-based payment arrangements		5,602,000
Stock based compensation and stock issued to officers as compensation	3,804,000	3,923,000
Net change in accrued interest receivable and other assets	2,101,000	(30,929,000)
Net change in other liabilities	(4,537,000)	(9,432,000)
Net cash provided by operating activities	170,597,000	124,055,000
Cash Flows from Investing Activities
Decrease/(increase) in short-term investments	(254,877,000)	119,785,000
Purchase of investment securities available-for-sale	(690,966,000)	(1,323,149,000)
Proceeds from sale of investment securities available-for-sale	415,543,000	1,033,195,000
Proceeds from repayments, maturities and calls of investment securities available-for-sale	585,285,000	232,253,000
Purchase of Federal Home Loan Bank stock	(1,650,000)
Redemptions of Federal Home Loan Bank stock		13,535,000
Net increase in loans	(853,453,000)	(702,595,000)
Purchase of premises and equipment	(3,166,000)	(2,628,000)
Proceeds from sales of premises and equipment	11,000
Proceeds from sales of other real estate owned	6,713,000	10,524,000
Investment in affordable housing and alternative energy partnerships	(59,844,000)	(46,349,000)
Acquisition, net of cash acquired		6,572,000
Net cash used in investing activities	(856,404,000)	(658,857,000)
Cash Flows from Financing Activities
Net increase in deposits	429,976,000	1,034,442,000
Net decrease in federal funds purchased and securities sold under agreements to repurchase	(50,000,000)	(50,000,000)
Advances from Federal Home Loan Bank	2,730,000,000	4,842,000,000
Repayment of Federal Home Loan Bank borrowings	(2,305,000,000)	(5,192,000,000)
Cash dividends paid	(42,570,000)	(30,690,000)
Purchases of treasury stock	(54,441,000)	(50,701,000)
Proceeds from shares issued under Dividend Reinvestment Plan	1,643,000	3,636,000
Proceeds from exercise of stock options	49,000	3,433,000
Taxes paid related to net share settlement of RSUs	(103,000)	(204,000)
Excess tax short-fall from share-based payment arrangements		(5,602,000)
Net cash provided by financing activities	709,554,000	554,314,000
Increase in cash and cash equivalents	23,747,000	19,512,000
Cash and cash equivalents, beginning of the period	180,130,000	176,830,000
Cash and cash equivalents, end of the period	203,877,000	196,342,000
Supplemental disclosure of cash flow information
Interest	61,212,000	52,614,000
Income taxes paid	31,717,000	67,776,000
Non-cash investing and financing activities:
Net change in unrealized holding gain on securities available-for-sale, net of tax	13,927,000	4,790,000
Net change in unrealized holding loss on cash flow hedge derivatives	(3,598,000)	(1,818,000)
Transfers of investment securities to available-for-sale from other assets		520,000
Transfers to other real estate owned from loans held for investment	2,698,000	3,914,000
Loans transferred from held for sale to held for investment, net	1,351,000
Loans to facilitate the sale of other real estate owned	2,616,000
Issuance of stock related to acquisition		$ 82,857,000