Fair Value (Assets and liabilities on recurring and non-recurring basis) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available-for-sale	$ 2,194,286	$ 2,959,912
Money Market Funds, at Carrying Value	13,205	3,863
Derivative Assets	21,889	9,317
Servicing Assets	10,795	10,454	9,695
Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available-for-sale	2,174,274	2,912,600
Securities purchased under agreements to resell	80,000	0
Derivative Assets	8,656	0
Derivative liabilities	(26,260)	(47,425)
Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available-for-sale	20,012	47,312
Derivative Assets	13,233	9,317
Servicing Assets	10,795	10,454
Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available-for-sale	2,194,286	2,959,912
Securities purchased under agreements to resell	80,000
Money Market Funds, at Carrying Value	13,205	3,863
Derivative Assets	21,889	9,317
Servicing Assets	10,795	10,454
Derivative liabilities	(38,967)	(56,787)
Total	2,281,208	2,926,759
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available-for-sale	0	0
Securities purchased under agreements to resell	0
Money Market Funds, at Carrying Value	13,205	3,863
Derivative Assets	0	0
Servicing Assets	0	0
Derivative liabilities	0	0
Total	13,205	3,863
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available-for-sale	2,174,274	2,912,600
Securities purchased under agreements to resell	80,000
Money Market Funds, at Carrying Value	0	0
Derivative Assets	8,656	0
Servicing Assets	0	0
Derivative liabilities	(26,260)	(47,425)
Total	2,236,670	2,865,175
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investment securities available-for-sale	20,012	47,312
Securities purchased under agreements to resell	0
Money Market Funds, at Carrying Value	0	0
Derivative Assets	13,233	9,317
Servicing Assets	10,795	10,454
Derivative liabilities	(12,707)	(9,362)
Total	31,333	57,721
Fair Value, Measurements, Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired commercial loans	35,917	46,364
Foreclosed real estate	39,400	27,679
Total	75,317	74,043
Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired commercial loans	0	0
Foreclosed real estate	0	0
Total	0	0
Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired commercial loans	0	0
Foreclosed real estate	0	0
Total	0	0
Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired commercial loans	35,917	46,364
Foreclosed real estate	39,400	27,679
Total	$ 75,317	$ 74,043