Investment Securities (Summary Of Available For Sale Investment Securities) (Details) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 3,350,355	$ 3,020,904
Gross Unrealized Gains	25,840	32,857
Gross Unrealized Losses	(21,522)	(12,355)
Fair Value	3,354,673	3,041,406
U.S. Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	43,149	42,636
Gross Unrealized Gains	383	190
Gross Unrealized Losses	0	0
Fair Value	43,532	42,826
U.S. Government Agency Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	24,505	26,426
Gross Unrealized Gains	763	898
Gross Unrealized Losses	0	0
Fair Value	25,268	27,324
Securities Issued By U.S. Government Sponsored Enterprises [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	126,947	81,332
Gross Unrealized Gains	920	710
Gross Unrealized Losses	0	0
Fair Value	127,867	82,042
Mortgage-Backed Securities Issued By U.S. Government Agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	176,856	177,678
Gross Unrealized Gains	2,012	2,578
Gross Unrealized Losses	(794)	(440)
Fair Value	178,074	179,816
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	2,416,229	2,250,897
Gross Unrealized Gains	12,780	19,915
Gross Unrealized Losses	(18,280)	(9,131)
Fair Value	2,410,729	2,261,681
Collateralized Mortgage Obligations Issued By U.S. Government Sponsored Enterprises [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	534,730	414,562
Gross Unrealized Gains	4,487	4,856
Gross Unrealized Losses	(1,949)	(2,342)
Fair Value	537,268	417,076
State And Municipal Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	4,566	5,024
Gross Unrealized Gains	120	183
Gross Unrealized Losses	(1)	(1)
Fair Value	4,685	5,206
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	3,228	3,228
Gross Unrealized Gains	4,375	$ 3,520
Gross Unrealized Losses	0
Fair Value	7,603	$ 6,748
Other Investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	20,145	19,121
Gross Unrealized Gains	0	7
Gross Unrealized Losses	(498)	(441)
Fair Value	$ 19,647	$ 18,687