Investment Securities (Amortized Cost And Estimated Fair Value By Contractual Maturity Of Investment Securities Available For Sale) (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012
Schedule of Available-for-sale Securities [Line Items]
Within One year, Amortized Cost	$ 45,241
1 to 5 Years, Amortized Cost	344,634
5 to 10 Years, Amortized Cost	1,271,530
More Than 10 years, Amortized Cost	1,492,120
No Stated Maturity, Amortized Cost	3,647
Total, Amortized Cost	3,157,172
Within One Year, Fair Value	46,738
1 to 5 Years, Fair Value	349,574
5 to 10 Years, Fair Value	1,290,935
More Than 10 years, Fair Value	1,538,372
No Stated Maturity, Fair Value	3,821
Total, Fair Value	3,229,440
U.S. Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Within One year, Amortized Cost	0
1 to 5 Years, Amortized Cost	356
5 to 10 Years, Amortized Cost	0
More Than 10 years, Amortized Cost	0
No Stated Maturity, Amortized Cost	0
Total, Amortized Cost	356
Within One Year, Fair Value	0
1 to 5 Years, Fair Value	356
5 to 10 Years, Fair Value	0
More Than 10 years, Fair Value	0
No Stated Maturity, Fair Value	0
Total, Fair Value	356
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	1,265
5 to 10 Years, Amortized Cost	32,512
More Than 10 years, Amortized Cost	2,029
No Stated Maturity, Amortized Cost	0
Total, Amortized Cost	35,806
Within One Year, Fair Value	0
1 to 5 Years, Fair Value	1,440
5 to 10 Years, Fair Value	34,371
More Than 10 years, Fair Value	2,436
No Stated Maturity, Fair Value	0
Total, Fair Value	38,247
Securities Issued By U.S. Government Sponsored Enterprises [Member]
Schedule of Available-for-sale Securities [Line Items]
Within One year, Amortized Cost	39,455
1 to 5 Years, Amortized Cost	325,251
5 to 10 Years, Amortized Cost	0
More Than 10 years, Amortized Cost	0
No Stated Maturity, Amortized Cost	0
Total, Amortized Cost	364,706
Within One Year, Fair Value	40,843
1 to 5 Years, Fair Value	329,256
5 to 10 Years, Fair Value	0
More Than 10 years, Fair Value	0
No Stated Maturity, Fair Value	0
Total, Fair Value	370,099
Mortgage-Backed Securities Issued By U.S. Government Agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Within One year, Amortized Cost	4
1 to 5 Years, Amortized Cost	332
5 to 10 Years, Amortized Cost	1
More Than 10 years, Amortized Cost	268,147
No Stated Maturity, Amortized Cost	0
Total, Amortized Cost	268,484
Within One Year, Fair Value	4
1 to 5 Years, Fair Value	352
5 to 10 Years, Fair Value	1
More Than 10 years, Fair Value	278,249
No Stated Maturity, Fair Value	0
Total, Fair Value	278,606
Mortgage-Backed Securities Issued By U.S. Government Sponsored Enterprises [Member]
Schedule of Available-for-sale Securities [Line Items]
Within One year, Amortized Cost	2,238
1 to 5 Years, Amortized Cost	9,564
5 to 10 Years, Amortized Cost	1,234,495
More Than 10 years, Amortized Cost	628,305
No Stated Maturity, Amortized Cost	0
Total, Amortized Cost	1,874,602
Within One Year, Fair Value	2,322
1 to 5 Years, Fair Value	10,039
5 to 10 Years, Fair Value	1,251,878
More Than 10 years, Fair Value	664,779
No Stated Maturity, Fair Value	0
Total, Fair Value	1,929,018
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	586,757
No Stated Maturity, Amortized Cost	0
Total, Amortized Cost	586,757
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	586,457
No Stated Maturity, Fair Value	0
Total, Fair Value	586,457
State And Municipal Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Within One year, Amortized Cost	2,544
1 to 5 Years, Amortized Cost	7,866
5 to 10 Years, Amortized Cost	4,522
More Than 10 years, Amortized Cost	3,882
No Stated Maturity, Amortized Cost	0
Total, Amortized Cost	18,814
Within One Year, Fair Value	2,568
1 to 5 Years, Fair Value	8,131
5 to 10 Years, Fair Value	4,685
More Than 10 years, Fair Value	4,162
No Stated Maturity, Fair Value	0
Total, Fair Value	19,546
Other Investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Within One year, Amortized Cost	1,000
1 to 5 Years, Amortized Cost	0
5 to 10 Years, Amortized Cost	0
More Than 10 years, Amortized Cost	3,000
No Stated Maturity, Amortized Cost	0
Total, Amortized Cost	4,000
Within One Year, Fair Value	1,001
1 to 5 Years, Fair Value	0
5 to 10 Years, Fair Value	0
More Than 10 years, Fair Value	2,289
No Stated Maturity, Fair Value	0
Total, Fair Value	3,290
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	3,647
Total, Amortized Cost	3,647
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	3,821
Total, Fair Value	$ 3,821