Borrowed Funds (Narrative) (Details) (USD $)	3 Months Ended	12 Months Ended
	Dec. 31, 2011 years	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Debt Instrument [Line Items]
Weighted average interest rate for short-term borrowings	0.25%	0.25%	0.45%
Interest expense recorded on FHLB advances		$ 86,600,000	$ 91,500,000	$ 93,700,000
Callable FHLB advances interest rates range, low	2.27%	2.27%
Callable FHLB advances interest rates range, high	4.76%	4.76%
FHLB advances modification amount	435,000,000
Extension of FHLB maturity dates, years	10
FHLB advances non-callable range low, years	3
FHLB advances non-callable range high, years	4
FHLB modified advances	150,000,000
Decline in weighted interest rate on FHLB borrowings	0.86%
Weighted average interest rate on FHLB borrowings	3.99%
Interest expense on securities sold under repurchase agreements		25,000,000	28,300,000	28,900,000
Subordinated notes, interest rate		5.00%
Subordinated note, due date		Jul. 15, 2015
Fair value of securities	1,500,000,000	1,500,000,000	1,500,000,000
FHLB [Member]
Debt Instrument [Line Items]
Weighted average interest rate for long-term borrowings	3.91%	3.91%	4.15%
Securities Sold Under Agreements To Repurchase [Member]
Debt Instrument [Line Items]
Weighted average interest rate for long-term borrowings	4.18%	4.18%	4.27%
Long-Term Borrowings [Member]
Debt Instrument [Line Items]
Advances with scheduled maturities beyond 2015	1,624,964,000	1,624,964,000
Long-term borrowings for securities sold under repurchase agreements	587,500,000	587,500,000	655,000,000
Subordinated notes	$ 100,000,000	$ 100,000,000	$ 100,000,000