Investment Securities (Amortized Cost And Estimated Fair Value By Contractual Maturity Of Investment Securities Available For Sale) (Details) $ in Thousands	Sep. 30, 2015 USD ($)
Schedule of Available-for-sale Securities [Line Items]
Within One year, Amortized Cost	$ 100,048
1 to 5 Years, Amortized Cost	79,221
5 to 10 Years, Amortized Cost	1,923,427
More Than 10 years, Amortized Cost	1,347,556
No Stated Maturity, Amortized Cost	6,389
Total, Amortized Cost	3,456,641
Within One Year, Fair Value	100,523
1 to 5 Years, Fair Value	80,502
5 to 10 Years, Fair Value	1,929,219
More Than 10 years, Fair Value	1,365,526
No Stated Maturity, Fair Value	11,562
Total, Fair Value	3,487,332
U.S. Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Within One year, Amortized Cost	18,287
1 to 5 Years, Amortized Cost	24,872
5 to 10 Years, Amortized Cost	0
More Than 10 years, Amortized Cost	0
No Stated Maturity, Amortized Cost	0
Total, Amortized Cost	43,159
Within One Year, Fair Value	18,287
1 to 5 Years, Fair Value	25,386
5 to 10 Years, Fair Value	0
More Than 10 years, Fair Value	0
No Stated Maturity, Fair Value	0
Total, Fair Value	43,673
U.S. Government Agency Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Within One year, Amortized Cost	0
1 to 5 Years, Amortized Cost	6,676
5 to 10 Years, Amortized Cost	6,420
More Than 10 years, Amortized Cost	0
No Stated Maturity, Amortized Cost	0
Total, Amortized Cost	13,096
Within One Year, Fair Value	0
1 to 5 Years, Fair Value	6,990
5 to 10 Years, Fair Value	6,811
More Than 10 years, Fair Value	0
No Stated Maturity, Fair Value	0
Total, Fair Value	13,801
Securities Issued By U.S. Government Sponsored Enterprises [Member]
Schedule of Available-for-sale Securities [Line Items]
Within One year, Amortized Cost	80,679
1 to 5 Years, Amortized Cost	46,055
5 to 10 Years, Amortized Cost	0
More Than 10 years, Amortized Cost	0
No Stated Maturity, Amortized Cost	0
Total, Amortized Cost	126,734
Within One Year, Fair Value	81,139
1 to 5 Years, Fair Value	46,461
5 to 10 Years, Fair Value	0
More Than 10 years, Fair Value	0
No Stated Maturity, Fair Value	0
Total, Fair Value	127,600
Mortgage-Backed Securities Issued By U.S. Government Agencies [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	20,052
More Than 10 years, Amortized Cost	188,733
No Stated Maturity, Amortized Cost	0
Total, Amortized Cost	208,785
Within One Year, Fair Value	0
1 to 5 Years, Fair Value	0
5 to 10 Years, Fair Value	20,441
More Than 10 years, Fair Value	190,414
No Stated Maturity, Fair Value	0
Total, Fair Value	210,855
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Schedule of Available-for-sale Securities [Line Items]
Within One year, Amortized Cost	0
1 to 5 Years, Amortized Cost	870
5 to 10 Years, Amortized Cost	1,881,955
More Than 10 years, Amortized Cost	648,718
No Stated Maturity, Amortized Cost	0
Total, Amortized Cost	2,531,543
Within One Year, Fair Value	0
1 to 5 Years, Fair Value	910
5 to 10 Years, Fair Value	1,886,916
More Than 10 years, Fair Value	660,267
No Stated Maturity, Fair Value	0
Total, Fair Value	2,548,093
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	0
More Than 10 years, Amortized Cost	505,498
No Stated Maturity, Amortized Cost	0
Total, Amortized Cost	505,498
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	510,620
No Stated Maturity, Fair Value	0
Total, Fair Value	510,620
State And Municipal Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Within One year, Amortized Cost	1,082
1 to 5 Years, Amortized Cost	748
5 to 10 Years, Amortized Cost	0
More Than 10 years, Amortized Cost	2,607
No Stated Maturity, Amortized Cost	0
Total, Amortized Cost	4,437
Within One Year, Fair Value	1,097
1 to 5 Years, Fair Value	755
5 to 10 Years, Fair Value	0
More Than 10 years, Fair Value	2,694
No Stated Maturity, Fair Value	0
Total, Fair Value	4,546
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	3,228
Total, Amortized Cost	3,228
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	8,471
Total, Fair Value	8,471
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	15,000
More Than 10 years, Amortized Cost	2,000
No Stated Maturity, Amortized Cost	3,161
Total, Amortized Cost	20,161
Within One Year, Fair Value	0
1 to 5 Years, Fair Value	0
5 to 10 Years, Fair Value	15,051
More Than 10 years, Fair Value	1,531
No Stated Maturity, Fair Value	3,091
Total, Fair Value	$ 19,673