Available-For-Sale Securities (Summary Of The Available-For-Sale Securities Portfolio) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012		Dec. 31, 2011		Mar. 31, 2011
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 1,866,314		$ 1,284,733
Gross unrealized gains	21,334		22,402
Gross unrealized losses	(18,304)		(15,338)
Fair Value	1,869,344		1,291,797		1,710,321
U.S. Treasury [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	23,063		16,028
Gross unrealized gains	128		145
Gross unrealized losses	(2)
Fair Value	23,189		16,173		96,160
U.S. Government Agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	682,847		760,533
Gross unrealized gains	4,082		5,596
Gross unrealized losses	(4,149)		(213)
Fair Value	682,780		765,916		795,854
Municipal [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	67,970		57,962
Gross unrealized gains	1,963		2,159
Gross unrealized losses	(18)		(23)
Fair Value	69,915		60,098		48,406
Corporate Notes And Other, Financial Issuers [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	148,492		149,229
Gross unrealized gains	2,569		1,914
Gross unrealized losses	(9,044)		(8,499)
Fair Value	142,017		142,644
Corporate Notes And Other, Other [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	26,475		27,070
Gross unrealized gains	329		287
Gross unrealized losses	(5)		(65)
Fair Value	26,799		27,292
Mortgage-Backed, Agency [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	846,380	[1]	206,549	[1]
Gross unrealized gains	11,866	[1]	12,078	[1]
Gross unrealized losses	(806)	[1]	(15)	[1]
Fair Value	857,440	[1]	218,612	[1]
Mortgage-Backed, Non-Agency CMOs [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	28,423	[1]	29,767	[1]
Gross unrealized gains	286	[1]	175	[1]
Gross unrealized losses	(1)	[1]	(3)	[1]
Fair Value	28,708	[1]	29,939	[1]
Other Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	42,664		37,595
Gross unrealized gains	111		48
Gross unrealized losses	(4,279)		(6,520)
Fair Value	$ 38,496		$ 31,123

[1] Consisting entirely of residential mortgage-backed securities, none of which are subprime.