Investment Securities (Maturities Table) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Securities Available for Sale
One year or less	$ 59,781
Over one year through five years	2,206,321
Over five years through ten years	899,078
Over ten years	101,677
Fair Value	3,266,857
Available-for-sale	3,273,174	2,920,971
Weighted Average Yield, one year or less	3.10%
Weighted Average Yield, over one year through five years	2.24%
Weighted Average Yield, over five years through ten years	2.85%
Weighted Average Yield, over ten years	2.26%
Weighted Average Yield, Total	2.42%
Available-for-sale Securities, Amortized Cost Basis	3,329,117	2,848,771
Weighted-Average Yield	2.42%
Available for Sale Securities, Debt Maturities, Weighted-Average Maturity	4 years 9 months 15 days
Securities Held to Maturity
One year or less	75,261
Over one year through five years	1,731,845
Over five years through ten years	842,899
Over ten years	174,235
Fair Value	2,824,240	630,799
Weighted Average Yield, one year or less	1.50%
Weighted Average Yield, over one year through five years	1.78%
Weighted Average Yield, over five years through ten years	2.38%
Weighted Average Yield, over ten years	5.40%
Weighted Average Yield, Total	2.17%
Held-to-maturity Securities, Amortized Cost before Other than Temporary Impairment	2,935,688	622,121
Held-to-maturity	2,935,688	622,121
Held to Maturity Securities Debt Maturities Weighted Average Yield	2.17%
Held to Maturity Securities Debt Maturities Weighted Average Maturity	5 years 6 months 1 day
U.S. Government agencies
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	23,652
Over ten years	0
Fair Value	23,652
Held-to-maturity Securities, Amortized Cost before Other than Temporary Impairment	25,000
Held-to-maturity	23,652
Held to Maturity Securities Debt Maturities Weighted Average Yield	1.43%
Held to Maturity Securities Debt Maturities Weighted Average Maturity	5 years 9 months 30 days
U.S. Treasury obligations
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	5,004
Over five years through ten years	0
Over ten years	0
Fair Value	5,004
Held-to-maturity Securities, Amortized Cost before Other than Temporary Impairment	5,000
Held-to-maturity	5,004
Held to Maturity Securities Debt Maturities Weighted Average Yield	0.26%
Held to Maturity Securities Debt Maturities Weighted Average Maturity	1 year 0 months 29 days
U.S. States and political subdivisions
Securities Available for Sale
One year or less	11,901
Over one year through five years	53,498
Over five years through ten years	166,913
Over ten years	30,055
Available-for-sale	262,367	268,204
Available-for-sale Securities, Amortized Cost Basis	258,787	253,198
Weighted-Average Yield	5.10%
Available for Sale Securities, Debt Maturities, Weighted-Average Maturity	6 years 11 months 13 days
Securities Held to Maturity
One year or less	75,261
Over one year through five years	45,746
Over five years through ten years	180,337
Over ten years	174,235
Fair Value	475,579
Held-to-maturity Securities, Amortized Cost before Other than Temporary Impairment	480,703	270,005
Held-to-maturity	475,579	275,061
Held to Maturity Securities Debt Maturities Weighted Average Yield	4.72%
Held to Maturity Securities Debt Maturities Weighted Average Maturity	10 years 11 months 16 days
Residential Mortgage Backed Securities Issued by US Government Sponsored Enterprises
Securities Available for Sale
One year or less	1,555
Over one year through five years	768,747
Over five years through ten years	199,620
Over ten years	0
Fair Value	969,922
Available-for-sale	969,922	1,107,063
Available-for-sale Securities, Amortized Cost Basis	962,687	1,058,005
Weighted-Average Yield	2.75%
Available for Sale Securities, Debt Maturities, Weighted-Average Maturity	4 years 2 months 17 days
Securities Held to Maturity
One year or less	0
Over one year through five years	351,715
Over five years through ten years	207,736
Over ten years	0
Fair Value	559,451
Held-to-maturity Securities, Amortized Cost before Other than Temporary Impairment	569,960
Held-to-maturity	559,451
Held to Maturity Securities Debt Maturities Weighted Average Yield	2.12%
Held to Maturity Securities Debt Maturities Weighted Average Maturity	5 years 3 months 23 days
Commercial Mortgage Backed Securities Issued by US Government Sponsored Enterprises
Securities Available for Sale
One year or less	16,944
Over one year through five years	19,237
Over five years through ten years	33,386
Over ten years	0
Fair Value	69,567
Available-for-sale	69,567	52,036
Available-for-sale Securities, Amortized Cost Basis	72,048	52,014
Weighted-Average Yield	2.09%
Available for Sale Securities, Debt Maturities, Weighted-Average Maturity	3 years 11 months 28 days
Securities Held to Maturity
One year or less	0
Over one year through five years	15,007
Over five years through ten years	40,399
Over ten years	0
Fair Value	55,406
Held-to-maturity Securities, Amortized Cost before Other than Temporary Impairment	56,596	33,165
Held-to-maturity	55,406	33,977
Held to Maturity Securities Debt Maturities Weighted Average Yield	1.79%
Held to Maturity Securities Debt Maturities Weighted Average Maturity	5 years 7 months 25 days
Residential Collateralized Mortgage-Backed Securities Issued by US Government Sponsored Enterprises
Securities Available for Sale
One year or less	4,830
Over one year through five years	1,245,303
Over five years through ten years	268,260
Over ten years	0
Fair Value	1,518,393
Available-for-sale	1,518,393	1,329,421
Available-for-sale Securities, Amortized Cost Basis	1,566,262	1,311,501
Weighted-Average Yield	1.86%
Available for Sale Securities, Debt Maturities, Weighted-Average Maturity	4 years 2 months 21 days
Securities Held to Maturity
One year or less	0
Over one year through five years	1,105,292
Over five years through ten years	277,622
Over ten years	0
Fair Value	1,382,914
Held-to-maturity Securities, Amortized Cost before Other than Temporary Impairment	1,464,732	123,563
Held-to-maturity	1,382,914	124,080
Held to Maturity Securities Debt Maturities Weighted Average Yield	1.56%
Held to Maturity Securities Debt Maturities Weighted Average Maturity	4 years 7 months 3 days
Residential Collateralized Mortgage-Backed Securities Issued by Non-US Government Agency
Securities Available for Sale
One year or less	0
Over one year through five years	9
Over five years through ten years	0
Over ten years	0
Fair Value	9
Available-for-sale	9	11
Available-for-sale Securities, Amortized Cost Basis	9	11
Weighted-Average Yield	3.65%
Available for Sale Securities, Debt Maturities, Weighted-Average Maturity	1 year 9 months 23 days
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
Fair Value	0
Held-to-maturity Securities, Amortized Cost before Other than Temporary Impairment	0
Held to Maturity Securities Debt Maturities Weighted Average Yield	0.00%
Commercial Collateralized Mortgage Backed Securities Issued by US Government Sponsored Enterprises
Securities Available for Sale
One year or less	0
Over one year through five years	79,688
Over five years through ten years	22,580
Over ten years	0
Fair Value	102,268
Available-for-sale	102,268	111,343
Available-for-sale Securities, Amortized Cost Basis	104,152	109,260
Weighted-Average Yield	1.65%
Available for Sale Securities, Debt Maturities, Weighted-Average Maturity	4 years 4 months 26 days
Securities Held to Maturity
One year or less	0
Over one year through five years	115,870
Over five years through ten years	113,153
Over ten years	0
Fair Value	229,023
Held-to-maturity Securities, Amortized Cost before Other than Temporary Impairment	240,069	98,924
Held-to-maturity	229,023	99,696
Held to Maturity Securities Debt Maturities Weighted Average Yield	2.27%
Held to Maturity Securities Debt Maturities Weighted Average Maturity	5 years 2 months 24 days
Collateralized Loan Obligations
Securities Available for Sale
One year or less	24,551
Over one year through five years	39,839
Over five years through ten years	208,319
Over ten years	20,978
Fair Value	293,687
Available-for-sale	293,687
Available-for-sale Securities, Amortized Cost Basis	297,259
Weighted-Average Yield	2.66%
Available for Sale Securities, Debt Maturities, Weighted-Average Maturity	6 years 2 months 17 days
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
Fair Value	0
Held-to-maturity Securities, Amortized Cost before Other than Temporary Impairment	0
Held to Maturity Securities Debt Maturities Weighted Average Yield	0.00%
Corporate bonds
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	50,644
Fair Value	50,644
Available-for-sale	50,644	49,652
Available-for-sale Securities, Amortized Cost Basis	61,596	61,541
Weighted-Average Yield	0.96%
Available for Sale Securities, Debt Maturities, Weighted-Average Maturity	13 years 9 months 23 days
Securities Held to Maturity
One year or less	0
Over one year through five years	93,211
Over five years through ten years	0
Over ten years	0
Fair Value	93,211
Held-to-maturity Securities, Amortized Cost before Other than Temporary Impairment	93,628	96,464
Held-to-maturity	$ 93,211	$ 97,985
Held to Maturity Securities Debt Maturities Weighted Average Yield	2.22%
Held to Maturity Securities Debt Maturities Weighted Average Maturity	4 years 0 months 14 days