Short-Term Borrowings and Long-Term Debt Short Term (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Short-term Debt [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	$ 1,800,000,000
Short-term Debt	868,399,000	597,033,000	674,077,000
Collateralized Borrowings Availability At Discount Window	1,900,000,000	1,700,000,000
Federal Funds Purchased [Member]
Short-term Debt [Line Items]
Short-term Debt	592,470,000	253,470,000	267,844,000
Short-term Debt, Maximum Month-end Outstanding Amount	636,562,000	381,093,000	506,567,000
Repurchase Agreements [Member]
Short-term Debt [Line Items]
Short-term Debt	156,238,000	186,735,000	204,800,000
Short-term Debt, Maximum Month-end Outstanding Amount	258,734,000	235,780,000	279,414,000
Notes Payable, Other Payables [Member]
Short-term Debt [Line Items]
Short-term Debt	119,691,000	156,828,000	201,433,000
Short-term Debt, Maximum Month-end Outstanding Amount	152,570,000	196,562,000	243,637,000
Other Debt Obligations [Member]
Short-term Debt [Line Items]
Short-term Debt	0	0	0
Short-term Debt, Maximum Month-end Outstanding Amount	$ 25,000,000	$ 0	$ 0