Parent Company Information (Schedule Of Condensed Statements Of Cash Flows) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Net Income	$ 133,653	$ 131,170	$ 116,061
Depreciation and amortization	16,380	15,850	15,316
Stock-based compensation	3,156	4,830	5,049
Net amortization of premiums and accretion of discounts on securities	11,871	12,443	9,592
(Gains) losses on securities transactions, net	(32,068)	(11,598)	(8,005)
Net impairment losses on securities recognized in earnings	19,968	4,642	6,352
Fair value of borrowings carried at fair value	(1,256)	5,841	15,828
Other assets	(34,977)	9,569	91,644
Net cash provided by operating activities	191,337	279,014	104,553
Sales	552,486	425,473	326,096
Maturities, calls and principal repayments	280,046	327,316	333,041
Net cash (used in) provided by investing activities	(192,841)	429,183	428,804
Redemption of preferred stock			(300,000)
Dividends paid to preferred shareholders			(12,980)
Dividends paid to common shareholders	(116,779)	(115,190)	(109,005)
Common stock issued, net	8,027	8,391	140,008
Net cash used in financing activities	14,267	(1,003,248)	(452,527)
Net change in cash and cash equivalents	12,763	(295,051)	80,830
Cash and cash equivalents at beginning of year	366,286	661,337	580,507
Cash and cash equivalents at end of year	379,049	366,286	661,337
Parent Company [Member]
Net Income	133,653	131,170	116,061
Equity in (undistributed) over distributed earnings of subsidiary	(28,273)	(79,766)	(15,543)
Depreciation and amortization	30	30	30
Stock-based compensation	3,156	4,830	5,049
Net amortization of premiums and accretion of discounts on securities	(56)	(51)	(54)
(Gains) losses on securities transactions, net		(106)
Net impairment losses on securities recognized in earnings			434
Fair value of borrowings carried at fair value	(1,256)	5,841	15,828
Other assets	535	(538)	(3,052)
Accrued expenses and other liabilities	132	(3,363)	(954)
Net cash provided by operating activities	107,921	58,047	117,799
Loan originations	(36,990)
Sales		94
Maturities, calls and principal repayments		1,250
Net cash (used in) provided by investing activities	(36,990)	1,344
Redemption of preferred stock			(300,000)
Dividends paid to preferred shareholders			(12,980)
Dividends paid to common shareholders	(116,779)	(115,190)	(109,005)
Common stock issued, net	8,027	8,391	140,008
Net cash used in financing activities	(108,752)	(106,799)	(281,977)
Net change in cash and cash equivalents	(37,821)	(47,408)	(164,178)
Cash and cash equivalents at beginning of year	80,549	127,957	292,135
Cash and cash equivalents at end of year	$ 42,728	$ 80,549	$ 127,957