CONSOLIDATED STATEMENTS OF CASH FLOWS (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
OPERATING ACTIVITIES
Net income	$ 122,717	$ 106,472	$ 91,002
Adjustments to reconcile net income to net cash provided by operating activities:
Provision for loan losses	17,500	22,200	31,510
Depreciation and amortization	40,847	42,931	39,376
Deferred income tax expense (benefit)	3,675	(197)	(13,226)
Net decrease (increase) in trading securities and other earning assets	2,378	(15,662)	(4,266)
Gains on sales of securities available for sale	(20,232)	(16,125)	(8,315)
(Gains) losses on sales of assets	(904)	175	(368)
Amortization of securities premiums, net of discount accretion	50,435	44,909	32,088
Originations of loans held for sale	(237,997)	(204,099)	(217,965)
Net gains on sales of loans held for sale	(2,010)	(1,598)	(1,379)
Proceeds from sales of loans held for sale	246,345	209,896	222,453
Issuance of equity awards	245	240	125
Equity based compensation	6,917	6,510	5,953
Changes in:
Accrued income	6,248	656	(11,704)
Accrued expenses and taxes	8,376	16,990	246
Other assets and liabilities, net	(20,796)	(255)	14,464
Net cash provided by operating activities	223,744	213,043	179,994
INVESTING ACTIVITIES
Proceeds from maturities of securities held to maturity	9,756	8,814	9,574
Proceeds from sales of securities available for sale	1,016,129	1,012,068	649,083
Proceeds from maturities of securities available for sale	1,691,293	1,561,960	1,994,810
Purchases of securities held to maturity	(39,642)	(34,788)	(16,193)
Purchases of securities available for sale	(3,561,042)	(3,008,900)	(3,421,255)
Net increase in loans	(738,343)	(407,232)	(215,442)
Net (increase) decrease in fed funds sold and resell agreements	(23,790)	169,098	94,589
Net decrease in interest bearing balances due from other financial institutions	129,076	20,117	114,570
Purchases of bank premises and equipment	(44,038)	(35,557)	(32,592)
Net cash received (paid) for acquisitions	17,597	(8,134)	(159,154)
Proceeds from sales of bank premises and equipment	1,473	182	2,793
Net cash provided by investing activities	(1,541,531)	(722,372)	(979,217)
FINANCING ACTIVITIES
Net increase in demand and savings deposits	1,737,072	1,286,818	655,039
Net decrease in time deposits	(272,627)	(145,648)	(160,936)
Net (decrease) increase in fed funds purchased and repurchase Agreements	(163,557)	(133,515)	156,735
Net change in short-term debt	(12,000)	(22,020)	4,548
Proceeds from long-term debt	1,029	500
Repayment of long-term debt	(1,679)	(4,055)	(15,416)
Payment of contingent consideration on acquisitions	(17,371)	(8,316)
Cash dividends paid	(33,787)	(31,801)	(30,328)
Net tax benefit related to equity compensation plans	359	79	152
Proceeds from exercise of stock options and sales of treasury shares	7,530	2,443	2,280
Purchases of treasury stock	(20,419)	(9,142)	(8,879)
Net cash provided by financing activities	1,224,550	935,343	603,195
(Decrease) increase in cash and due from banks	(93,237)	426,014	(196,028)
Cash and due from banks at beginning of year	1,459,631	1,033,617	1,229,645
Cash and due from banks at end of year	1,366,394	1,459,631	1,033,617
Supplemental disclosures:
Income taxes paid	44,074	41,041	48,116
Total interest paid	$ 20,975	$ 28,148	$ 40,128