Investment Securities (Summary Of Available For Sale Investment Securities) (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 3,456,641	$ 3,020,904
Gross Unrealized Gains	38,300	32,857
Gross Unrealized Losses	(7,609)	(12,355)
Fair Value	3,487,332	3,041,406
U.S. Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	43,159	42,636
Gross Unrealized Gains	514	190
Gross Unrealized Losses	0	0
Fair Value	43,673	42,826
U.S. Government Agency Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	13,096	26,426
Gross Unrealized Gains	705	898
Gross Unrealized Losses	0	0
Fair Value	13,801	27,324
Securities Issued By U.S. Government Sponsored Enterprises [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	126,734	81,332
Gross Unrealized Gains	866	710
Gross Unrealized Losses	0	0
Fair Value	127,600	82,042
Mortgage-Backed Securities Issued By U.S. Government Agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	208,785	177,678
Gross Unrealized Gains	2,458	2,578
Gross Unrealized Losses	(388)	(440)
Fair Value	210,855	179,816
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	2,531,543	2,250,897
Gross Unrealized Gains	22,314	19,915
Gross Unrealized Losses	(5,764)	(9,131)
Fair Value	2,548,093	2,261,681
Collateralized Mortgage Obligations Issued By U.S. Government Sponsored Enterprises [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	505,498	414,562
Gross Unrealized Gains	6,039	4,856
Gross Unrealized Losses	(917)	(2,342)
Fair Value	510,620	417,076
State And Municipal Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	4,437	5,024
Gross Unrealized Gains	110	183
Gross Unrealized Losses	(1)	(1)
Fair Value	4,546	5,206
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	3,228	3,228
Gross Unrealized Gains	5,243	$ 3,520
Gross Unrealized Losses	0
Fair Value	8,471	$ 6,748
Other Investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	20,161	19,121
Gross Unrealized Gains	51	7
Gross Unrealized Losses	(539)	(441)
Fair Value	$ 19,673	$ 18,687