Investment Securities (Maturities Table) (Details) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2014	Dec. 31, 2013	Sep. 30, 2013
Schedule of Available-for-Sale and Held-to-Maturity Securities [Line Items]
Available for Sale Securities, Debt Maturities, Weighted-Average Mat	4 years 4 months 15 days
Securities Available for Sale
One year or less	$ 48,965
Available for Sale Securities Debt Maturities Maturity Period of One Year or Less Weighted Average Yield	3.59%
Over one year through five years	2,638,864
Available for Sale Securities Debt Maturities Maturity Period over One Year Through Five Years Weighted Average Yield	2.22%
Over five years through ten years	683,254
Available for Sale Securities Debt Maturities Maturity Period over Five Years Through Ten Years Weighted Average Yield	3.17%
Over ten years	86,491
Available for Sale Securities Debt Maturities Maturity Period over Ten Years Weighted Average Yield	2.02%
Weighted-Average Yield	2.42%
Securities Held to Maturity
One year or less	95,398
Held to Maturity Securities Debt Maturities Maturity Period of One Year or Less Weighted Average Yield	1.70%
Over one year through five years	2,125,604
Held to Maturity Securities Debt Maturities Maturity Period over One Year Through Five Years Weighted Average Yield	1.85%
Over five years through ten years	528,742
Held to Maturity Securities Debt Maturities Maturity Period over Five Years Through Ten Years Weighted Average Yield	2.90%
Over ten years	197,428
Held-to-maturity Securities, Fair Value	2,947,172	2,824,240	2,658,433
Held-to-maturity Securities, Amortized Cost before Other than Temporary Impairment	3,002,262	2,935,688	2,749,934
Weighted Average Yield	2.27%
Held to Maturity Securities Debt Maturities-Weighted Aver Maturity	4 years 11 months 13 days
Held to Maturity Securities Debt Maturities Maturity Period over Ten Years Weighted Average Yield	5.47%
US Government Agencies Debt Securities
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	0
Fair Value	0
Amortized Cost	0
Weighted-Average Yield	0.00%
Securities Held to Maturity
One year or less	0
Over one year through five years	0
Over five years through ten years	24,244
Over ten years	0
Held-to-maturity Securities, Amortized Cost before Other than Temporary Impairment	25,000	25,000	25,000
Weighted Average Yield	1.43%
Held to Maturity Securities Debt Maturities-Weighted Aver Maturity	5 years 0 months 29 days
US Treasury Securities
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	0
Fair Value	0
Amortized Cost	0
Weighted-Average Yield	0.00%
Securities Held to Maturity
One year or less	5,003
Over one year through five years	0
Over five years through ten years	0
Over ten years	0
Held-to-maturity Securities, Amortized Cost before Other than Temporary Impairment	5,000	5,000	5,000
Weighted Average Yield	0.25%
Held to Maturity Securities Debt Maturities-Weighted Aver Maturity	0 years 4 months 0 days
U.S. States and political subdivisions debt securities
Schedule of Available-for-Sale and Held-to-Maturity Securities [Line Items]
Available for Sale Securities, Debt Maturities, Weighted-Average Mat	6 years 2 months 13 days
Securities Available for Sale
One year or less	12,583
Over one year through five years	66,352
Over five years through ten years	126,235
Over ten years	31,897
Weighted-Average Yield	5.23%
Securities Held to Maturity
One year or less	84,201
Over one year through five years	68,480
Over five years through ten years	200,709
Over ten years	197,428
Held-to-maturity Securities, Amortized Cost before Other than Temporary Impairment	539,014	480,703	453,230
Weighted Average Yield	4.70%
Held to Maturity Securities Debt Maturities-Weighted Aver Maturity	9 years 7 months 25 days
Residential Mortgage Backed Securities Issued by US Government Sponsored Enterprises
Schedule of Available-for-Sale and Held-to-Maturity Securities [Line Items]
Available for Sale Securities, Debt Maturities, Weighted-Average Mat	3 years 11 months 24 days
Securities Available for Sale
One year or less	2,969
Over one year through five years	820,635
Over five years through ten years	172,783
Over ten years	0
Weighted-Average Yield	2.63%
Securities Held to Maturity
One year or less	0
Over one year through five years	478,503
Over five years through ten years	122,333
Over ten years	0
Held-to-maturity Securities, Amortized Cost before Other than Temporary Impairment	602,220	569,960	377,980
Weighted Average Yield	2.15%
Held to Maturity Securities Debt Maturities-Weighted Aver Maturity	4 years 7 months 11 days
Commercial Mortgage Backed Securities Issued by US Government Sponsored Enterprises
Schedule of Available-for-Sale and Held-to-Maturity Securities [Line Items]
Available for Sale Securities, Debt Maturities, Weighted-Average Mat	3 years 11 months 13 days
Securities Available for Sale
One year or less	16,749
Over one year through five years	35,549
Over five years through ten years	32,466
Over ten years	0
Weighted-Average Yield	2.12%
Securities Held to Maturity
One year or less	6,194
Over one year through five years	14,874
Over five years through ten years	43,988
Over ten years	0
Held-to-maturity Securities, Amortized Cost before Other than Temporary Impairment	65,704	56,596	50,179
Weighted Average Yield	2.08%
Held to Maturity Securities Debt Maturities-Weighted Aver Maturity	4 years 11 months 2 days
Residential Collateralized Mortgage-Backed Securities Issued by US Government Sponsored Enterprises
Schedule of Available-for-Sale and Held-to-Maturity Securities [Line Items]
Available for Sale Securities, Debt Maturities, Weighted-Average Mat	3 years 9 months 26 days
Securities Available for Sale
One year or less	9,163
Over one year through five years	1,561,512
Over five years through ten years	29,642
Over ten years	0
Weighted-Average Yield	1.98%
Securities Held to Maturity
One year or less	0
Over one year through five years	1,312,389
Over five years through ten years	46,838
Over ten years	0
Held-to-maturity Securities, Amortized Cost before Other than Temporary Impairment	1,415,421	1,464,732	1,523,792
Weighted Average Yield	1.60%
Held to Maturity Securities Debt Maturities-Weighted Aver Maturity	4 years 1 month 5 days
Residential Collateralized Mortgage-Backed Securities Issued by Non-US Government Agency
Schedule of Available-for-Sale and Held-to-Maturity Securities [Line Items]
Available for Sale Securities, Debt Maturities, Weighted-Average Mat	1 year 11 months 27 days
Securities Available for Sale
One year or less	0
Over one year through five years	7
Over five years through ten years	0
Over ten years	0
Weighted-Average Yield	3.48%
Securities Held to Maturity
One year or less	0
Over one year through five years	0
Over five years through ten years	0
Over ten years	0
Held-to-maturity Securities, Fair Value	0
Held-to-maturity Securities, Amortized Cost before Other than Temporary Impairment	0
Weighted Average Yield	0.00%
Commercial Collateralized Mortgage Backed Securities Issued by US Government Sponsored Enterprises
Schedule of Available-for-Sale and Held-to-Maturity Securities [Line Items]
Available for Sale Securities, Debt Maturities, Weighted-Average Mat	3 years 8 months 9 days
Securities Available for Sale
One year or less	0
Over one year through five years	154,809
Over five years through ten years	39,208
Over ten years	0
Weighted-Average Yield	1.97%
Securities Held to Maturity
One year or less	0
Over one year through five years	159,582
Over five years through ten years	90,630
Over ten years	0
Held-to-maturity Securities, Amortized Cost before Other than Temporary Impairment	258,436	240,069	220,410
Weighted Average Yield	2.28%
Held to Maturity Securities Debt Maturities-Weighted Aver Maturity	4 years 9 months 12 days
Collateralized Loan Obligations
Schedule of Available-for-Sale and Held-to-Maturity Securities [Line Items]
Available for Sale Securities, Debt Maturities, Weighted-Average Mat	6 years 0 months 22 days
Securities Available for Sale
One year or less	7,501
Over one year through five years	0
Over five years through ten years	282,920
Over ten years	0
Weighted-Average Yield	2.61%
Securities Held to Maturity
One year or less	0
Over one year through five years	0
Over five years through ten years	0
Over ten years	0
Held-to-maturity Securities, Fair Value	0
Held-to-maturity Securities, Amortized Cost before Other than Temporary Impairment	0
Weighted Average Yield	0.00%
Corporate debt securities
Schedule of Available-for-Sale and Held-to-Maturity Securities [Line Items]
Available for Sale Securities, Debt Maturities, Weighted-Average Mat	13 years 0 months 22 days
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	54,594
Weighted-Average Yield	0.95%
Securities Held to Maturity
One year or less	0
Over one year through five years	91,776
Over five years through ten years	0
Over ten years	0
Held-to-maturity Securities, Amortized Cost before Other than Temporary Impairment	$ 91,467	$ 93,628	$ 94,343
Weighted Average Yield	2.22%
Held to Maturity Securities Debt Maturities-Weighted Aver Maturity	3 years 3 months 12 days