Investment Securities (Amortized Cost And Estimated Fair Value By Contractual Maturity Of Investment Securities Available For Sale) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Within One year, Amortized Cost	$ 49,104
1 to 5 Years, Amortized Cost	96,341
5 to 10 Years, Amortized Cost	1,989,730
More Than 10 years, Amortized Cost	999,250
No Stated Maturity, Amortized Cost	5,857
Total, Amortized Cost	3,140,282
Within One Year, Fair Value	49,490
1 to 5 Years, Fair Value	97,823
5 to 10 Years, Fair Value	1,975,865
More Than 10 years, Fair Value	999,732
No Stated Maturity, Fair Value	9,492
Total, Fair Value	3,132,402
U.S. Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Within One year, Amortized Cost	17,792
1 to 5 Years, Amortized Cost	0
5 to 10 Years, Amortized Cost	0
More Than 10 years, Amortized Cost	0
No Stated Maturity, Amortized Cost	0
Total, Amortized Cost	17,792
Within One Year, Fair Value	17,792
1 to 5 Years, Fair Value	0
5 to 10 Years, Fair Value	0
More Than 10 years, Fair Value	0
No Stated Maturity, Fair Value	0
Total, Fair Value	17,792
U.S. Government Agency Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Within One year, Amortized Cost	114
1 to 5 Years, Amortized Cost	9,097
5 to 10 Years, Amortized Cost	24,065
More Than 10 years, Amortized Cost	0
No Stated Maturity, Amortized Cost	0
Total, Amortized Cost	33,276
Within One Year, Fair Value	114
1 to 5 Years, Fair Value	9,427
5 to 10 Years, Fair Value	24,852
More Than 10 years, Fair Value	0
No Stated Maturity, Fair Value	0
Total, Fair Value	34,393
Securities Issued By U.S. Government Sponsored Enterprises [Member]
Schedule of Available-for-sale Securities [Line Items]
Within One year, Amortized Cost	30,070
1 to 5 Years, Amortized Cost	81,981
5 to 10 Years, Amortized Cost	0
More Than 10 years, Amortized Cost	0
No Stated Maturity, Amortized Cost	0
Total, Amortized Cost	112,051
Within One Year, Fair Value	30,426
1 to 5 Years, Fair Value	82,894
5 to 10 Years, Fair Value	0
More Than 10 years, Fair Value	0
No Stated Maturity, Fair Value	0
Total, Fair Value	113,320
Mortgage-Backed Securities Issued By U.S. Government Agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Within One year, Amortized Cost	26
1 to 5 Years, Amortized Cost	1
5 to 10 Years, Amortized Cost	0
More Than 10 years, Amortized Cost	170,299
No Stated Maturity, Amortized Cost	0
Total, Amortized Cost	170,326
Within One Year, Fair Value	26
1 to 5 Years, Fair Value	1
5 to 10 Years, Fair Value	0
More Than 10 years, Fair Value	169,192
No Stated Maturity, Fair Value	0
Total, Fair Value	169,219
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Schedule of Available-for-sale Securities [Line Items]
Within One year, Amortized Cost	346
1 to 5 Years, Amortized Cost	2,890
5 to 10 Years, Amortized Cost	1,965,354
More Than 10 years, Amortized Cost	427,079
No Stated Maturity, Amortized Cost	0
Total, Amortized Cost	2,395,669
Within One Year, Fair Value	366
1 to 5 Years, Fair Value	3,084
5 to 10 Years, Fair Value	1,950,681
More Than 10 years, Fair Value	431,833
No Stated Maturity, Fair Value	0
Total, Fair Value	2,385,964
Collateralized Mortgage-Backed Securities Issued By U.S. Government Sponsored Enterprises [Member]
Schedule of Available-for-sale Securities [Line Items]
Within One year, Amortized Cost	0
1 to 5 Years, Amortized Cost	0
5 to 10 Years, Amortized Cost	22
More Than 10 years, Amortized Cost	397,032
No Stated Maturity, Amortized Cost	0
Total, Amortized Cost	397,054
Within One Year, Fair Value	0
1 to 5 Years, Fair Value	0
5 to 10 Years, Fair Value	22
More Than 10 years, Fair Value	393,887
No Stated Maturity, Fair Value	0
Total, Fair Value	393,909
State And Municipal Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Within One year, Amortized Cost	756
1 to 5 Years, Amortized Cost	2,372
5 to 10 Years, Amortized Cost	289
More Than 10 years, Amortized Cost	2,840
No Stated Maturity, Amortized Cost	0
Total, Amortized Cost	6,257
Within One Year, Fair Value	766
1 to 5 Years, Fair Value	2,417
5 to 10 Years, Fair Value	310
More Than 10 years, Fair Value	2,961
No Stated Maturity, Fair Value	0
Total, Fair Value	6,454
Securities With No Stated Maturity (Equity Securities) [Member]
Schedule of Available-for-sale Securities [Line Items]
Within One year, Amortized Cost	0
1 to 5 Years, Amortized Cost	0
5 to 10 Years, Amortized Cost	0
More Than 10 years, Amortized Cost	0
No Stated Maturity, Amortized Cost	3,768
Total, Amortized Cost	3,768
Within One Year, Fair Value	0
1 to 5 Years, Fair Value	0
5 to 10 Years, Fair Value	0
More Than 10 years, Fair Value	0
No Stated Maturity, Fair Value	7,508
Total, Fair Value	7,508
Other Investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Within One year, Amortized Cost	0
1 to 5 Years, Amortized Cost	0
5 to 10 Years, Amortized Cost	0
More Than 10 years, Amortized Cost	2,000
No Stated Maturity, Amortized Cost	2,089
Total, Amortized Cost	4,089
Within One Year, Fair Value	0
1 to 5 Years, Fair Value	0
5 to 10 Years, Fair Value	0
More Than 10 years, Fair Value	1,859
No Stated Maturity, Fair Value	1,984
Total, Fair Value	$ 3,843