Commitments and Contingencies (Details) (USD $)	12 Months Ended
	Dec. 31, 2011 claim	Dec. 31, 2010
Commitments and Contingencies
Total outstanding loan balances	$ 13,791,239,000	$ 13,244,150,000
Maximum liability under indemnity in connection with liquidation of an investment acquired	23,000,000
Fair value of guarantee obligations	300,000
Number of legal claims with unfavorable judgment	2
Unfavorable judgments through arbitration on legal claims	7,200,000
Loss covered by entity's insurance policies	5,300,000
Net charges included in other operating expense in noninterest expense	1,200,000	700,000
Commitments and Contingencies
Commitments
Off-balance sheet loan commitments
Commitments and Contingencies
Commitments	5,670,000,000	4,520,000,000
Letters of Credit
Commitments and Contingencies
Commitments	723,500,000	603,800,000
Standby letters of credit, included within letters of credit
Commitments and Contingencies
Commitments	708,900,000	588,900,000
Commercial letters of credit, including within letters of credit
Commitments and Contingencies
Commitments	14,700,000	14,900,000
Private equity fund and alternative investment
Commitments and Contingencies
Commitments	68,900,000	65,900,000
Commitments, funded amount	57,900,000	52,300,000
Affordable housing fund
Commitments and Contingencies
Commitments	$ 39,600,000	$ 23,300,000