Investment Securities Available for Sale (Amortized Cost And Estimated Fair Value By Contractual Maturity Of Investment Securities Available For Sale) (Details) $ in Thousands	Dec. 31, 2015 USD ($)
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost, Within One year	$ 99,770
Amortized Cost, 1 to 5 Years	79,042
Amortized Cost, 5 to 10 Years	1,688,836
Amortized Cost, More Than 10 years	1,721,745
Amortized Cost, Amortized Cost, No Stated Maturity	6,405
Total Amortized Cost	3,595,798
Fair Value, Within One year	99,957
Fair Value, 1 to 5 Years	79,752
Fair Value, 5 to 10 Years	1,674,807
Fair Value, More Than 10 years	1,720,557
Fair Value, No Stated Maturity	12,745
Total Fair Value	3,587,818
U.S. Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost, Within One year	18,243
Amortized Cost, 1 to 5 Years	24,882
Amortized Cost, 5 to 10 Years	0
Amortized Cost, More Than 10 years	0
Amortized Cost, Amortized Cost, No Stated Maturity	0
Total Amortized Cost	43,125
Fair Value, Within One year	18,243
Fair Value, 1 to 5 Years	25,114
Fair Value, 5 to 10 Years	0
Fair Value, More Than 10 years	0
Fair Value, No Stated Maturity	0
Total Fair Value	43,357
U.S. Government Agency Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost, Within One year	0
Amortized Cost, 1 to 5 Years	6,676
Amortized Cost, 5 to 10 Years	6,411
Amortized Cost, More Than 10 years	0
Amortized Cost, Amortized Cost, No Stated Maturity	0
Total Amortized Cost	13,087
Fair Value, Within One year	0
Fair Value, 1 to 5 Years	6,907
Fair Value, 5 to 10 Years	6,716
Fair Value, More Than 10 years	0
Fair Value, No Stated Maturity	0
Total Fair Value	13,623
Securities Issued By U.S. Government Sponsored Enterprises [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost, Within One year	80,460
Amortized Cost, 1 to 5 Years	46,060
Amortized Cost, 5 to 10 Years	0
Amortized Cost, More Than 10 years	0
Amortized Cost, Amortized Cost, No Stated Maturity	0
Total Amortized Cost	126,520
Fair Value, Within One year	80,634
Fair Value, 1 to 5 Years	46,275
Fair Value, 5 to 10 Years	0
Fair Value, More Than 10 years	0
Fair Value, No Stated Maturity	0
Total Fair Value	126,909
Mortgage-Backed Securities Issued By U.S. Government Agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost, Within One year	0
Amortized Cost, 1 to 5 Years	0
Amortized Cost, 5 to 10 Years	18,745
Amortized Cost, More Than 10 years	191,040
Amortized Cost, Amortized Cost, No Stated Maturity	0
Total Amortized Cost	209,785
Fair Value, Within One year	0
Fair Value, 1 to 5 Years	0
Fair Value, 5 to 10 Years	18,999
Fair Value, More Than 10 years	191,005
Fair Value, No Stated Maturity	0
Total Fair Value	210,004
Mortgage-Backed Securities Issued By U.S. Government Sponsored Enterprises [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost, Within One year	0
Amortized Cost, 1 to 5 Years	725
Amortized Cost, 5 to 10 Years	1,648,680
Amortized Cost, More Than 10 years	995,702
Amortized Cost, Amortized Cost, No Stated Maturity	0
Total Amortized Cost	2,645,107
Fair Value, Within One year	0
Fair Value, 1 to 5 Years	755
Fair Value, 5 to 10 Years	1,634,107
Fair Value, More Than 10 years	995,557
Fair Value, No Stated Maturity	0
Total Fair Value	2,630,419
Collateralized Mortgage-Backed Securities Issued By U.S. Government Sponsored Enterprises [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost, Within One year	0
Amortized Cost, 1 to 5 Years	0
Amortized Cost, 5 to 10 Years	0
Amortized Cost, More Than 10 years	530,426
Amortized Cost, Amortized Cost, No Stated Maturity	0
Total Amortized Cost	530,426
Fair Value, Within One year	0
Fair Value, 1 to 5 Years	0
Fair Value, 5 to 10 Years	0
Fair Value, More Than 10 years	529,597
Fair Value, No Stated Maturity	0
Total Fair Value	529,597
State And Municipal Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost, Within One year	1,067
Amortized Cost, 1 to 5 Years	699
Amortized Cost, 5 to 10 Years	0
Amortized Cost, More Than 10 years	2,577
Amortized Cost, Amortized Cost, No Stated Maturity	0
Total Amortized Cost	4,343
Fair Value, Within One year	1,080
Fair Value, 1 to 5 Years	701
Fair Value, 5 to 10 Years	0
Fair Value, More Than 10 years	2,653
Fair Value, No Stated Maturity	0
Total Fair Value	4,434
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost, Within One year	0
Amortized Cost, 1 to 5 Years	0
Amortized Cost, 5 to 10 Years	0
Amortized Cost, More Than 10 years	0
Amortized Cost, Amortized Cost, No Stated Maturity	3,228
Total Amortized Cost	3,228
Fair Value, Within One year	0
Fair Value, 1 to 5 Years	0
Fair Value, More Than 10 years	0
Fair Value, No Stated Maturity	9,672
Total Fair Value	9,672
Other Investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost, Within One year	0
Amortized Cost, 1 to 5 Years	0
Amortized Cost, 5 to 10 Years	15,000
Amortized Cost, More Than 10 years	2,000
Amortized Cost, Amortized Cost, No Stated Maturity	3,177
Total Amortized Cost	20,177
Fair Value, Within One year	0
Fair Value, 1 to 5 Years	0
Fair Value, 5 to 10 Years	14,985
Fair Value, More Than 10 years	1,745
Fair Value, No Stated Maturity	3,073
Total Fair Value	$ 19,803