Consolidated Statements of Cash Flows - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Cash Flows from Operating Activities
Net income	$ 161,109,000	$ 137,830,000	$ 123,735,000
Adjustments to reconcile net income to net cash provided by operating activities:
Credit for loan losses	(11,400,000)	(10,800,000)	(3,000,000)
Provision/(Reversal) for losses on other real estate owned	547,000	1,619,000	(2,122,000)
Deferred tax liability/(benefit)	2,004,000	31,304,000	(15,114,000)
Depreciation and amortization	7,574,000	7,868,000	11,347,000
Net gains on sale and transfers of other real estate owned	(2,012,000)	(4,065,000)	(1,793,000)
Net gains on sale of loans	(786,000)	(395,000)	(879,000)
Proceeds from sale of loans	32,530,000	19,287,000	42,573,000
Originations of loans held for sale	(37,447,000)	(19,865,000)	(41,694,000)
Income associated with debt redemption		(555,000)
Amortization on alternative energy partnerships, venture capital and other investments	25,058,000	436,000	409,000
Write-down on impaired securities	3,875,000	820,000
Gain on sales and calls of securities	(526,000)	(7,568,000)	(27,362,000)
Other non-cash interest (income)/expense	(332,000)	(137,000)	1,100,000
Amortization of security premiums, net	5,140,000	2,849,000	4,425,000
Excess tax short-fall from stock options	5,348,000	1,285,000	2,509,000
Stock based and stock issued to officers and directors compensation expense	4,950,000	4,190,000	3,213,000
Noncontrolling interest			(592,000)
Net change in accrued interest receivable and other assets	(3,429,000)	(2,776,000)	23,291,000
Net change in other liabilities	(15,506,000)	(11,256,000)	(4,973,000)
Net cash provided by operating activities	176,697,000	150,071,000	115,073,000
Cash Flows from Investing Activities
(Increase)/decrease in short-term investments	(47,266,000)	32,260,000	(104,955,000)
Purchase of investment securities available-for-sale	(295,497,000)	(885,782,000)	(350,130,000)
Proceeds from maturity and call of investment securities available-for-sale	165,000,000	585,776,000	180,088,000
Proceeds from sale of investment securities available-for-sale	385,234,000	160,451,000	575,358,000
Purchase of mortgage-backed securities available-for-sale	(1,280,870,000)	(307,617,000)	(676,529,000)
Proceeds from repayment and sale of mortgage-backed securities available-for-sale	749,219,000	768,236,000	669,658,000
Proceeds from maturity and call of investment securities held-to-maturity			50,973,000
Purchase of Federal Home Loan Bank stock		(18,164,000)
Redemption of Federal Home Loan Bank stock	13,535,000	12,379,000	16,272,000
Net increase in loans	(829,501,000)	(824,558,000)	(676,245,000)
Purchase of premises and equipment	(3,518,000)	(4,777,000)	(6,182,000)
Proceeds from sales of premises and equipment	602,000
Proceeds from sales of other real estate owned	12,154,000	29,880,000	19,411,000
Increase in investment in affordable housing and alternative energy partnerships	(53,235,000)	(7,445,000)	(9,525,000)
Acquisition, net of cash acquired	6,572,000
Net cash used in investing activities	(1,177,571,000)	(459,361,000)	(311,806,000)
Cash Flows from Financing Activities
Net increase in deposits	1,305,255,000	802,281,000	596,964,000
Net decrease in federal funds purchased and securities sold under agreements to repurchase	(50,000,000)	(350,000,000)	(450,000,000)
Advances from Federal Home Loan Bank	5,092,000,000	9,822,400,000	2,402,000,000
Repayment of Federal Home Loan Bank borrowings	(5,242,000,000)	(9,918,600,000)	(2,027,000,000)
Cash dividends	(45,283,000)	(23,104,000)	(12,606,000)
Purchase of treasury stock	(59,412,000)
Redemption of Series B preferred stock			(258,000,000)
Redemption of noncontrolling interest			(8,638,000)
Repayment of subordinated debt			(50,000,000)
Repayment of long-term debt and other borrowings		(1,445,000)
Proceeds from shares issued to Dividend Reinvestment Plan	4,175,000	2,848,000	605,000
Proceeds from exercise of stock options	5,014,000	128,000	14,755,000
Taxes paid related to net share settlement of RSUs	(227,000)	(850,000)
Excess tax short-fall from share-based payment arrangements	(5,348,000)	(1,285,000)	(2,509,000)
Net cash provided by financing activities	1,004,174,000	332,373,000	205,571,000
Increase in cash and cash equivalents	3,300,000	23,083,000	8,838,000
Cash and cash equivalents, beginning of the year	176,830,000	153,747,000	144,909,000
Cash and cash equivalents, end of the year	180,130,000	176,830,000	153,747,000
Cash paid during the year for:
Interest	72,870,000	78,366,000	84,848,000
Income taxes	69,074,000	60,225,000	55,521,000
Non-cash investing and financing activities:
Net change in unrealized holding (loss)/gain on securities available-for-sale, net of tax	(2,259,000)	26,557,000	(30,194,000)
Net change in unrealized losses on interest rate swaps designated as cash flow hedges	(598,000)	(2,397,000)
Transfers to short-term investments from trading securities		4,936,000
Transfers to investment securities available-for-sale at fair value from held-to-maturity			722,466,000
Transfers to other real estate owned from loans held for investment	866,000	4,970,000	22,171,000
Loans transferred to loans held for sale	6,684,000	973,000
Loans to facilitate the sale of other real estate owned		413,000	$ 75,000
Issuance of stock related to acquisition	82,857,000
Goodwill	372,189,000	$ 316,340,000
Asia Bancshares [Member]
Non-cash investing and financing activities:
Cash and cash equivalents	63,579,000
Securities available-for-sale	2,370,000
Loans	419,219,000
Premises and equipment	13,291,000
Other real estate owned	3,048,000
Goodwill	55,849,000
Core deposit intangible	1,302,000
Accrued interest receivable and other assets	2,884,000
Total assets acquired	561,542,000
Deposits	420,623,000
Accrued interest payable and other liabilities	1,056,000
Total liabilities assumed	421,679,000
Net assets acquired	139,863,000
Cash paid	57,006,000
Fair value of common stock issued	82,857,000
Total consideration paid	$ 139,863,000