Investment Securities (Schedule Of Investments Within The Available For Sale Portfolio That Had Unrealized Losses) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Jun. 30, 2014	Jun. 30, 2013
Schedule of Investments [Line Items]
Less than 12 months, Fair Value	$ 471,296	$ 1,426,567
Less than 12 months, Unrealized Losses	(2,385)	(32,659)
12 months or longer, Fair Value	1,113,455	15,967
12 months or longer, Unrealized Losses	(33,328)	(157)
Total Fair Value	1,584,751	1,442,534
Total Unrealized Losses	(35,713)	(32,816)
Collateralized Mortgage Obligations [Member]
Schedule of Investments [Line Items]
Less than 12 months, Fair Value	437,212	1,233,820
Less than 12 months, Unrealized Losses	(2,276)	(28,365)
12 months or longer, Fair Value	1,004,964	15,967
12 months or longer, Unrealized Losses	(31,789)	(157)
Total Fair Value	1,442,176	1,249,787
Total Unrealized Losses	(34,065)	(28,522)
Mortgage Backed Securities Issued By U S Government Sponsored Enterprises [Member]
Schedule of Investments [Line Items]
Less than 12 months, Fair Value	34,041	192,747
Less than 12 months, Unrealized Losses	(83)	(4,294)
12 months or longer, Fair Value	108,491	0
12 months or longer, Unrealized Losses	(1,539)	0
Total Fair Value	142,532	192,747
Total Unrealized Losses	(1,622)	(4,294)
Total debt securities
Schedule of Investments [Line Items]
Less than 12 months, Fair Value	471,253
Less than 12 months, Unrealized Losses	(2,359)
12 months or longer, Fair Value	1,113,455
12 months or longer, Unrealized Losses	(33,328)
Total Fair Value	1,584,708
Total Unrealized Losses	(35,687)
Equity Securities [Member]
Schedule of Investments [Line Items]
Less than 12 months, Fair Value	43
Less than 12 months, Unrealized Losses	(26)
12 months or longer, Fair Value	0
12 months or longer, Unrealized Losses	0
Total Fair Value	43
Total Unrealized Losses	$ (26)