Investment Securities (Available For Sale Securities Unrealized Gains And Losses, By Security Type) (Details) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Investment [Line Items]
Amortized Cost	$ 9,107,330	$ 9,386,302
Gross unreailzed gain in accumulated other comprehensive income at period end	156,178	172,642
Gross unreailzed losses in accumulated other comprehensive income at period end	(41,687)	(35,384)
Fair Value	9,221,821	9,523,560
U.S. Government And Federal Agency Obligations [Member]
Investment [Line Items]
Amortized Cost	427,621	497,336
Gross unreailzed gain in accumulated other comprehensive income at period end	11,597	9,095
Gross unreailzed losses in accumulated other comprehensive income at period end	(4,352)	(5,024)
Fair Value	434,866	501,407
Government-Sponsored Enterprise Obligations [Member]
Investment [Line Items]
Amortized Cost	888,270	968,574
Gross unreailzed gain in accumulated other comprehensive income at period end	4,462	2,593
Gross unreailzed losses in accumulated other comprehensive income at period end	(6,231)	(8,040)
Fair Value	886,501	963,127
State And Municipal Obligations [Member]
Investment [Line Items]
Amortized Cost	1,807,584	1,789,215
Gross unreailzed gain in accumulated other comprehensive income at period end	22,700	32,340
Gross unreailzed losses in accumulated other comprehensive income at period end	(13,183)	(8,354)
Fair Value	1,817,101	1,813,201
Agency Mortgage-Backed Securities [Member]
Investment [Line Items]
Amortized Cost	2,531,365	2,523,377
Gross unreailzed gain in accumulated other comprehensive income at period end	63,083	75,923
Gross unreailzed losses in accumulated other comprehensive income at period end	(6,755)	(5,592)
Fair Value	2,587,693	2,593,708
Non-Agency Mortgage-Backed Securities [Member]
Investment [Line Items]
Amortized Cost	682,114	372,911
Gross unreailzed gain in accumulated other comprehensive income at period end	11,079	11,061
Gross unreailzed losses in accumulated other comprehensive income at period end	(2,255)	(1,228)
Fair Value	690,938	382,744
Asset-Backed Securities [Member]
Investment [Line Items]
Amortized Cost	2,494,905	3,090,174
Gross unreailzed gain in accumulated other comprehensive income at period end	7,410	6,922
Gross unreailzed losses in accumulated other comprehensive income at period end	(3,809)	(5,103)
Fair Value	2,498,506	3,091,993
Total Mortgage And Asset-Backed Securities [Member]
Investment [Line Items]
Amortized Cost	5,708,384	5,986,462
Gross unreailzed gain in accumulated other comprehensive income at period end	81,572	93,906
Gross unreailzed losses in accumulated other comprehensive income at period end	(12,819)	(11,923)
Fair Value	5,777,137	6,068,445
Other Debt Securities [Member]
Investment [Line Items]
Amortized Cost	269,793	140,784
Gross unreailzed gain in accumulated other comprehensive income at period end	416	420
Gross unreailzed losses in accumulated other comprehensive income at period end	(5,102)	(2,043)
Fair Value	265,107	139,161
Equity Securities [Member]
Investment [Line Items]
Amortized Cost	5,678	3,931
Gross unreailzed gain in accumulated other comprehensive income at period end	35,431	34,288
Gross unreailzed losses in accumulated other comprehensive income at period end	0	0
Fair Value	$ 41,109	$ 38,219