Investment Securities (Available For Sale Securities Unrealized Gains And Losses, By Security Type) (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Investment [Line Items]
Amortized Cost	$ 9,331,750	$ 9,386,302
Gross unreailzed gain in accumulated other comprehensive income at period end	171,127	172,642
Gross unreailzed losses in accumulated other comprehensive income at period end	(29,918)	(35,384)
Fair Value	9,472,959	9,523,560
U.S. Government And Federal Agency Obligations [Member]
Investment [Line Items]
Amortized Cost	420,702	497,336
Gross unreailzed gain in accumulated other comprehensive income at period end	5,930	9,095
Gross unreailzed losses in accumulated other comprehensive income at period end	(6,233)	(5,024)
Fair Value	420,399	501,407
Government-Sponsored Enterprise Obligations [Member]
Investment [Line Items]
Amortized Cost	857,149	968,574
Gross unreailzed gain in accumulated other comprehensive income at period end	7,809	2,593
Gross unreailzed losses in accumulated other comprehensive income at period end	(2,749)	(8,040)
Fair Value	862,209	963,127
State And Municipal Obligations [Member]
Investment [Line Items]
Amortized Cost	1,820,236	1,789,215
Gross unreailzed gain in accumulated other comprehensive income at period end	33,416	32,340
Gross unreailzed losses in accumulated other comprehensive income at period end	(6,493)	(8,354)
Fair Value	1,847,159	1,813,201
Agency Mortgage-Backed Securities [Member]
Investment [Line Items]
Amortized Cost	2,508,870	2,523,377
Gross unreailzed gain in accumulated other comprehensive income at period end	69,477	75,923
Gross unreailzed losses in accumulated other comprehensive income at period end	(2,512)	(5,592)
Fair Value	2,575,835	2,593,708
Non-Agency Mortgage-Backed Securities [Member]
Investment [Line Items]
Amortized Cost	805,560	372,911
Gross unreailzed gain in accumulated other comprehensive income at period end	12,285	11,061
Gross unreailzed losses in accumulated other comprehensive income at period end	(648)	(1,228)
Fair Value	817,197	382,744
Asset-Backed Securities [Member]
Investment [Line Items]
Amortized Cost	2,585,088	3,090,174
Gross unreailzed gain in accumulated other comprehensive income at period end	7,444	6,922
Gross unreailzed losses in accumulated other comprehensive income at period end	(7,844)	(5,103)
Fair Value	2,584,688	3,091,993
Total Mortgage And Asset-Backed Securities [Member]
Investment [Line Items]
Amortized Cost	5,899,518	5,986,462
Gross unreailzed gain in accumulated other comprehensive income at period end	89,206	93,906
Gross unreailzed losses in accumulated other comprehensive income at period end	(11,004)	(11,923)
Fair Value	5,977,720	6,068,445
Other Debt Securities [Member]
Investment [Line Items]
Amortized Cost	328,468	140,784
Gross unreailzed gain in accumulated other comprehensive income at period end	979	420
Gross unreailzed losses in accumulated other comprehensive income at period end	(3,439)	(2,043)
Fair Value	326,008	139,161
Equity Securities [Member]
Investment [Line Items]
Amortized Cost	5,677	3,931
Gross unreailzed gain in accumulated other comprehensive income at period end	33,787	34,288
Gross unreailzed losses in accumulated other comprehensive income at period end	0	0
Fair Value	$ 39,464	$ 38,219