Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014
Cash flows from operating activities:
Net income	$ 30,341us-gaap_NetIncomeLoss	$ 33,835us-gaap_NetIncomeLoss
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	5,078	4,972
Stock-based compensation	2,479us-gaap_ShareBasedCompensation	2,178us-gaap_ShareBasedCompensation
Provision for credit losses	0	3,998
Net amortization of premiums and accretion of discounts on securities and borrowings	8,371	6,715
Amortization of other intangible assets	2,393us-gaap_AmortizationOfIntangibleAssets	2,351us-gaap_AmortizationOfIntangibleAssets
(Gains) losses on securities transactions, net	(2,416)us-gaap_GainLossOnSaleOfSecuritiesNet	8us-gaap_GainLossOnSaleOfSecuritiesNet
Proceeds from sales of loans held for sale	38,568	32,771
Gains on sales of loans, net	(598)us-gaap_GainLossOnSalesOfLoansNet	(913)us-gaap_GainLossOnSalesOfLoansNet
Originations of loans held for sale	(17,716)	(26,984)
(Gains) losses on sales of assets, net	(281)us-gaap_GainsLossesOnSalesOfAssets	148us-gaap_GainsLossesOnSalesOfAssets
FDIC loss-share receivable (excluding reimbursements)	3,920	76
Net change in:
Trading securities	14,233	9
Cash surrender value of bank owned life insurance	(1,764)us-gaap_BankOwnedLifeInsuranceIncome	(1,408)us-gaap_BankOwnedLifeInsuranceIncome
Accrued interest receivable	743	(322)
Other assets	(37,584)	15,010
Accrued expenses and other liabilities	8,104	(37,242)
Net cash provided by operating activities	53,871	35,202
Cash flows from investing activities:
Net loan originations	(122,279)	(150,592)
Loans purchased	(139,935)	(19,084)
Investment securities held to maturity:
Purchases	(145,973)	(177,462)
Sales	11,666	0
Maturities, calls and principal repayments	85,798	93,818
Investment securities available for sale:
Purchases	(8,034)	(5,964)
Sales	13,974	0
Maturities, calls and principal repayments	38,678	50,081
Proceeds from sales of real estate property and equipment	4,551	5,977
Purchases of real estate property and equipment	(3,216)	(5,673)
Reimbursements from the FDIC	1,954	1,424
Net cash used in investing activities	(262,816)	(207,475)
Cash flows from financing activities:
Net change in deposits	182,627us-gaap_IncreaseDecreaseInDeposits	(51,277)us-gaap_IncreaseDecreaseInDeposits
Net change in short-term borrowings	(12,915)	255,655
Cash dividends paid to common shareholders	(25,512)us-gaap_PaymentsOfDividendsCommonStock	(21,957)us-gaap_PaymentsOfDividendsCommonStock
Common stock (purchased) issued, net	(948)	286
Net cash provided by financing activities	143,252	182,707
Net change in cash and cash equivalents	(65,693)	10,434
Cash and cash equivalents at beginning of year	830,407	369,168
Cash and cash equivalents at end of period	764,714	379,602
Supplemental disclosures of cash flow information:
Interest on deposits and borrowings	41,978us-gaap_InterestPaid	42,133us-gaap_InterestPaid
Federal and state income taxes	29,550us-gaap_IncomeTaxesPaid	11,368us-gaap_IncomeTaxesPaid
Supplemental schedule of non-cash investing activities:
Transfer of loans to other real estate owned	1,944	3,508
Transfer of loans to loans held for sale	$ 0	$ 27,329

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The aggregate expense charged against earnings to allocate the cost of intangible assets (nonphysical assets not used in production) in a systematic and rational manner to the periods expected to benefit from such assets. As a noncash expense, this element is added back to net income when calculating cash provided by or used in operations using the indirect method.