Investment Securities (Schedule Of Investments Within The Available For Sale Portfolio That Had Unrealized Losses) (Details) - USD ($) $ in Thousands	6 Months Ended	12 Months Ended
	Jun. 30, 2017	Dec. 31, 2016
Schedule of Investments [Line Items]
Less than 12 months, Fair Value	$ 2,581,164	$ 2,971,604
Less than 12 months, Unrealized Losses	(29,339)	(42,920)
12 months or longer, Fair Value	128,377	116,527
12 months or longer, Unrealized Losses	(4,565)	(4,885)
Total Fair Value	2,709,541	3,088,131
Total Unrealized Losses	(33,904)	(47,805)
Government Agency Issued Collateralized Mortgage Obligations ("CMO")
Schedule of Investments [Line Items]
Less than 12 months, Fair Value	981,771	1,059,471
Less than 12 months, Unrealized Losses	(14,899)	(19,052)
12 months or longer, Fair Value	128,377	116,527
12 months or longer, Unrealized Losses	(4,565)	(4,885)
Total Fair Value	1,110,148	1,175,998
Total Unrealized Losses	(19,464)	(23,937)
Government Agency Issued Mortgage-Backed Securities ("MBS")
Schedule of Investments [Line Items]
Less than 12 months, Fair Value	1,599,386	1,912,126
Less than 12 months, Unrealized Losses	(14,438)	(23,866)
12 months or longer, Fair Value	0	0
12 months or longer, Unrealized Losses	0	0
Total Fair Value	1,599,386	1,912,126
Total Unrealized Losses	(14,438)	(23,866)
Total debt securities
Schedule of Investments [Line Items]
Less than 12 months, Fair Value	2,581,157	2,971,597
Less than 12 months, Unrealized Losses	(29,337)	(42,918)
12 months or longer, Fair Value	128,377	116,527
12 months or longer, Unrealized Losses	(4,565)	(4,885)
Total Fair Value	2,709,534	3,088,124
Total Unrealized Losses	(33,902)	(47,803)
Equity
Schedule of Investments [Line Items]
Less than 12 months, Fair Value	7	7
Less than 12 months, Unrealized Losses	(2)	(2)
12 months or longer, Fair Value	0	0
12 months or longer, Unrealized Losses	0	0
Total Fair Value	7	7
Total Unrealized Losses	$ (2)	$ (2)