Fair Value Measurements Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Investment securities available for sale:
Total investment securities available for sale	$ 4,854,319	$ 4,926,758
Trading Assets	49,732	70,711
Fair Value, Inputs, Level 1 [Member]
Investment securities available for sale:
Total investment securities available for sale	2,894	3,845
Fair Value, Inputs, Level 2 [Member]
Investment securities available for sale:
Total investment securities available for sale	4,850,914	4,922,433
Fair Value, Inputs, Level 3 [Member]
Investment securities available for sale:
Total investment securities available for sale	511	480
Fair Value, Measurements, Recurring [Member]
Investment securities available for sale:
Total investment securities available for sale	4,854,319	4,926,758
Trading Assets	75,153	82,125
Liabilities, Fair Value Disclosure [Abstract]
Derivatives (other liabilities)	62,857	80,110
Fair Value, Measurements, Recurring [Member] | US Treasury Securities [Member]
Investment securities available for sale:
Total investment securities available for sale	1,004	1,004
Fair Value, Measurements, Recurring [Member] | Obligations of state and political subdivisions (municipal securities) [Member]
Investment securities available for sale:
Total investment securities available for sale	730,233	801,188
Fair Value, Measurements, Recurring [Member] | Government-Sponsored Enterprise (GSE) [Member]
Investment securities available for sale:
Total investment securities available for sale	3,605,030	3,798,155
Fair Value, Measurements, Recurring [Member] | Private Label [Member]
Investment securities available for sale:
Total investment securities available for sale	3,439	6,149
Fair Value, Measurements, Recurring [Member] | Commercial Mortgage Backed Securities [Member]
Investment securities available for sale:
Total investment securities available for sale	431,252	228,166
Fair Value, Measurements, Recurring [Member] | Other Debt And Other Equity Securities [Member]
Investment securities available for sale:
Total investment securities available for sale	83,361	92,096
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Investment securities available for sale:
Total investment securities available for sale	2,894	3,845
Trading Assets	0	0
Liabilities, Fair Value Disclosure [Abstract]
Derivatives (other liabilities)	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | US Treasury Securities [Member]
Investment securities available for sale:
Total investment securities available for sale	1,004	1,004
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Obligations of state and political subdivisions (municipal securities) [Member]
Investment securities available for sale:
Total investment securities available for sale	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Government-Sponsored Enterprise (GSE) [Member]
Investment securities available for sale:
Total investment securities available for sale	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Private Label [Member]
Investment securities available for sale:
Total investment securities available for sale	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Commercial Mortgage Backed Securities [Member]
Investment securities available for sale:
Total investment securities available for sale	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member] | Other Debt And Other Equity Securities [Member]
Investment securities available for sale:
Total investment securities available for sale	1,890	2,841
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Investment securities available for sale:
Total investment securities available for sale	4,850,914	4,922,433
Trading Assets	54,840	74,331
Liabilities, Fair Value Disclosure [Abstract]
Derivatives (other liabilities)	57,706	79,963
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | US Treasury Securities [Member]
Investment securities available for sale:
Total investment securities available for sale	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Obligations of state and political subdivisions (municipal securities) [Member]
Investment securities available for sale:
Total investment securities available for sale	730,233	801,188
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Government-Sponsored Enterprise (GSE) [Member]
Investment securities available for sale:
Total investment securities available for sale	3,605,030	3,798,155
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Private Label [Member]
Investment securities available for sale:
Total investment securities available for sale	3,439	6,149
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Commercial Mortgage Backed Securities [Member]
Investment securities available for sale:
Total investment securities available for sale	431,252	228,166
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member] | Other Debt And Other Equity Securities [Member]
Investment securities available for sale:
Total investment securities available for sale	80,960	88,775
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Investment securities available for sale:
Total investment securities available for sale	511	480
Trading Assets	20,313	7,794
Liabilities, Fair Value Disclosure [Abstract]
Derivatives (other liabilities)	5,151	147
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | US Treasury Securities [Member]
Investment securities available for sale:
Total investment securities available for sale	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Obligations of state and political subdivisions (municipal securities) [Member]
Investment securities available for sale:
Total investment securities available for sale	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Government-Sponsored Enterprise (GSE) [Member]
Investment securities available for sale:
Total investment securities available for sale	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Private Label [Member]
Investment securities available for sale:
Total investment securities available for sale	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Commercial Mortgage Backed Securities [Member]
Investment securities available for sale:
Total investment securities available for sale	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member] | Other Debt And Other Equity Securities [Member]
Investment securities available for sale:
Total investment securities available for sale	$ 511	$ 480