Investment Securities (Summary Of Available For Sale Investment Securities) (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012		Dec. 31, 2011
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 3,507,196	[1]	$ 3,613,797	[1]
Gross Unrealized Gains	68,787		79,137
Gross Unrealized Losses	(5,637)		(2,809)
Fair Value	3,570,346		3,690,125
U.S. Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	307	[1]	426	[1]
Gross Unrealized Gains	0		0
Gross Unrealized Losses	0		0
Fair Value	307		426
U.S. Government Agency Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	37,238	[1]	37,489	[1]
Gross Unrealized Gains	2,442		3,004
Gross Unrealized Losses	0		0
Fair Value	39,680		40,493
Securities Issued By U.S. Government Sponsored Enterprises [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	559,306	[1]	667,707	[1]
Gross Unrealized Gains	5,248		8,333
Gross Unrealized Losses	(28)		(619)
Fair Value	564,526		675,421
Mortgage-Backed Securities Issued By U.S. Government Agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	272,813	[1]	266,682	[1]
Gross Unrealized Gains	7,303		19,071
Gross Unrealized Losses	(71)		0
Fair Value	280,045		285,753
Mortgage-Backed Securities Issued By U.S. Government Sponsored Enterprises [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	2,006,398	[1]	1,955,988	[1]
Gross Unrealized Gains	50,229		46,275
Gross Unrealized Losses	0		(257)
Fair Value	2,056,627		2,002,006
Collateralized Mortgage Obligations Issued By U.S. Government Sponsored Enterprises [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	602,109	[1]	651,379	[1]
Gross Unrealized Gains	2,785		1,646
Gross Unrealized Losses	(4,728)		(1,525)
Fair Value	600,166		651,500
State And Municipal Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	20,378	[1]	24,530	[1]
Gross Unrealized Gains	739		808
Gross Unrealized Losses	(20)		(20)
Fair Value	21,097		25,318
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	3,647	[1]	4,147	[1]
Gross Unrealized Gains	39		0
Gross Unrealized Losses	0		(388)
Fair Value	3,686		3,759
Other Investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	5,000	[1]	5,449	[1]
Gross Unrealized Gains	2		0
Gross Unrealized Losses	(790)		0
Fair Value	$ 4,212		$ 5,449

[1] Amortized cost is adjusted for other-than-temporary impairment charges in 2012 and 2011, which have been recognized on the consolidated statements of operations in the applicable period, and were considered inconsequential.