Investment Securities (Maturities Table) (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013
Securities Available for Sale
One year or less	$ 57,249
Over one year through five years	2,086,750
Over five years through ten years	1,061,212
Over ten years	87,687
Fair Value	3,292,898
Weighted Average Yield, one year or less	4.06%
Weighted Average Yield, over one year through five years	2.32%
Weighted Average Yield, over five years through ten years	2.44%
Weighted Average Yield, over ten years	2.17%
Weighted Average Yield, Total	2.38%
Amortized Cost	3,305,257
Weighted-Average Yield	2.38%
Weighted-Average Maturity	4.74
Securities Held to Maturity
One year or less	51,941
Over one year through five years	1,310,116
Over five years through ten years	932,338
Over ten years	192,676
Fair Value	2,487,071
Weighted Average Yield, one year or less	3.50%
Weighted Average Yield, over one year through five years	1.56%
Weighted Average Yield, over five years through ten years	0.20%
Weighted Average Yield, over ten years	3.47%
Weighted Average Yield, Total	1.91%
Amortized Cost	2,551,860
Weighted Average Yield	1.91%
Weighted-Average Maturity	5.73
US Government Agencies Debt Securities [Member]
Securities Held to Maturity
One year or less	0
Over one year through five years	0
Over five years through ten years	23,807
Over ten years	0
Fair Value	23,807
Amortized Cost	25,000
Weighted Average Yield	1.43%
Weighted-Average Maturity	6.33
US Treasury Securities [Member]
Securities Held to Maturity
One year or less	0
Over one year through five years	4,999
Over five years through ten years	0
Over ten years	0
Fair Value	4,999
Amortized Cost	4,999
Weighted Average Yield	0.62%
Weighted-Average Maturity	1.58
U.S. States and political subdivisions [Member]
Securities Available for Sale
One year or less	16,178
Over one year through five years	50,151
Over five years through ten years	175,056
Over ten years	36,549
Fair Value	277,934
Amortized Cost	272,254
Weighted-Average Yield	4.95%
Weighted-Average Maturity	7.19
Securities Held to Maturity
One year or less	51,941
Over one year through five years	42,404
Over five years through ten years	144,676
Over ten years	192,676
Fair Value	431,697
Amortized Cost	436,860
Weighted Average Yield	3.29%
Weighted-Average Maturity	11.60
Residential Mortgage Backed Securities Issued by US Government Sponsored Enterprises [Member]
Securities Available for Sale
One year or less	3,011
Over one year through five years	747,924
Over five years through ten years	324,993
Over ten years	0
Fair Value	1,075,928
Amortized Cost	1,058,323
Weighted-Average Yield	2.74%
Weighted-Average Maturity	4.12
Securities Held to Maturity
One year or less	0
Over one year through five years	88,609
Over five years through ten years	157,179
Over ten years	0
Fair Value	245,788
Amortized Cost	253,839
Weighted Average Yield	1.41%
Weighted-Average Maturity	4.96
Commercial Mortgage Backed Securities Issued by US Government Sponsored Enterprises [Member]
Securities Available for Sale
One year or less	17,460
Over one year through five years	0
Over five years through ten years	39,037
Over ten years	0
Fair Value	56,497
Amortized Cost	58,609
Weighted-Average Yield	2.11%
Weighted-Average Maturity	4.42
Securities Held to Maturity
One year or less	0
Over one year through five years	5,054
Over five years through ten years	44,679
Over ten years	0
Fair Value	49,733
Amortized Cost	50,352
Weighted Average Yield	1.47%
Weighted-Average Maturity	5.97
Residential Collateralized Mortgage-Backed Securities Issued by US Government Sponsored Enterprises [Member]
Securities Available for Sale
One year or less	13,062
Over one year through five years	1,198,392
Over five years through ten years	355,274
Over ten years	0
Fair Value	1,566,728
Amortized Cost	1,586,576
Weighted-Average Yield	1.81%
Weighted-Average Maturity	4.22
Securities Held to Maturity
One year or less	0
Over one year through five years	1,041,822
Over five years through ten years	426,945
Over ten years	0
Fair Value	1,468,767
Amortized Cost	1,510,374
Weighted Average Yield	1.51%
Weighted-Average Maturity	4.70
Residential Collateralized Mortgage-Backed Securities Issued by Non-US Government Agency [Member]
Securities Available for Sale
One year or less	0
Over one year through five years	10
Over five years through ten years	0
Over ten years	0
Fair Value	10
Amortized Cost	10
Weighted-Average Yield	3.84%
Weighted-Average Maturity	1.52
Commercial Collateralized Mortgage Backed Securities Issued by US Government Sponsored Enterprises [Member]
Securities Available for Sale
One year or less	0
Over one year through five years	78,705
Over five years through ten years	27,863
Over ten years	0
Fair Value	106,568
Amortized Cost	108,000
Weighted-Average Yield	1.81%
Weighted-Average Maturity	4.51
Securities Held to Maturity
One year or less	0
Over one year through five years	61,831
Over five years through ten years	106,268
Over ten years	0
Fair Value	168,099
Amortized Cost	175,384
Weighted Average Yield	2.95%
Weighted-Average Maturity	6.29
Collateralized Loan Obligations [Member]
Securities Available for Sale
One year or less	7,538
Over one year through five years	11,568
Over five years through ten years	138,989
Over ten years	0
Fair Value	158,095
Amortized Cost	159,916
Weighted-Average Yield	2.33%
Weighted-Average Maturity	6.44
Corporate debt securities [Member]
Securities Available for Sale
One year or less	0
Over one year through five years	0
Over five years through ten years	0
Over ten years	51,138
Fair Value	51,138
Amortized Cost	61,569
Weighted-Average Yield	0.99%
Weighted-Average Maturity	14.31
Securities Held to Maturity
One year or less	0
Over one year through five years	65,397
Over five years through ten years	28,784
Over ten years	0
Fair Value	94,181
Amortized Cost	$ 95,052
Weighted Average Yield	2.22%
Weighted-Average Maturity	4.54