Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($)	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Cash Flows from Operating Activities
Net income	$ 137,480,000	$ 100,356,000
Adjustments to reconcile net income to net cash provided by operating activities:
Reversal for credit losses	(3,000,000)	(2,500,000)
Provision for losses on other real estate owned		483,000
Deferred tax liability	2,432,000	12,227,000
Depreciation and amortization	3,868,000	3,504,000
Net gains on sale and transfer of other real estate owned	(459,000)	(317,000)
Proceeds from sales of loans	8,000,000	7,500,000
Amortization on alternative energy partnerships, venture capital and other investments	(405,000)	1,682,000
Net loss on sales and calls of securities		438,000
Amortization/accretion of security premiums/discounts, net	1,719,000	1,293,000
Unrealized loss on equity securities	4,971,000
Stock based compensation and stock issued to officers as compensation	4,054,000	3,107,000
Net change in accrued interest receivable and other assets	(8,043,000)	603,000
Gain on acquisition	(340,000)
Net change in other liabilities	(129,000)	1,857,000
Net cash provided by operating activities	150,148,000	130,233,000
Cash Flows from Investing Activities
Purchase of investment securities available-for-sale	(448,805,000)	(349,550,000)
Proceeds from sale of investment securities available-for-sale		99,541,000
Proceeds from repayments, maturities and calls of investment securities available-for-sale	257,339,000	198,619,000
Purchase of Federal Home Loan Bank stock	(5,430,000)
Redemptions of Federal Home Loan Bank stock	11,265,000
Net increase in loans	(474,900,000)	(369,751,000)
Purchase of premises and equipment	(2,706,000)	(1,718,000)
Proceeds from sales of other real estate owned	2,785,000	1,399,000
Net (increase)/decrease in investment in affordable housing and alternative energy partnerships	(19,201,000)	(16,685,000)
Net cash used for investing activities	(679,653,000)	(438,145,000)
Cash Flows from Financing Activities
Net increase/(decrease) in deposits	414,198,000	(211,228,000)
Net decrease in federal funds purchased and securities sold under agreements to repurchase	(50,000,000)	(200,000,000)
Advances from Federal Home Loan Bank	2,450,000,000	795,000,000
Repayment of Federal Home Loan Bank borrowings	(2,400,000,000)	(670,000,000)
Cash dividends paid	(38,966,000)	(33,524,000)
Proceeds from issuance of other borrowings	20,000,000
Proceeds from shares issued under Dividend Reinvestment Plan	1,325,000	1,233,000
Proceeds from exercise of stock options	838,000	877,000
Taxes paid related to net share settlement of RSUs	(3,550,000)	(5,118,000)
Net cash provided by (used in) financing activities	393,845,000	(322,760,000)
Decrease in cash and cash equivalents	(135,660,000)	(630,672,000)
Cash and cash equivalents, beginning of the period	539,801,000	1,185,084,000
Cash and cash equivalents, end of the period	404,141,000	554,412,000
Supplemental disclosure of cash flow information
Interest	49,606,000	39,259,000
Income taxes paid	31,589,000	30,096,000
Non-cash investing and financing activities:
Net change in unrealized holding loss on securities available-for-sale, net of tax	(14,265,000)	2,546,000
Net change in unrealized holding loss on cash flow hedge derivatives	2,929,000	(251,000)
Transfers to other real estate owned from loans held for investment	$ 715,000	$ 726,000