Derivative Instruments (Narrative) (Details) (USD $) | 3 Months Ended | 9 Months Ended | |||
|---|---|---|---|---|---|
Sep. 30, 2011 | Sep. 30, 2010 | Sep. 30, 2011 | Sep. 30, 2010 | Dec. 31, 2010 | |
| Other secured liabilities | $ 14,000,000 | ||||
| Loans and leases receivable, collateral for secured borrowings | 14,250,000 | ||||
| Other secured assets | 14,250,000 | ||||
| Gain or loss on derivative transactions, fair value | (17,819,000) | (7,021,000) | (16,913,000) | 34,446,000 | |
Interest Rate Contract [Member] | |||||
| Notional amount of interest rate derivative purchase contracts | 4,500,000,000 | 4,500,000,000 | 2,200,000,000 | ||
| Notional amount of interest rate derivative sale contracts | 298,000,000 | 298,000,000 | 209,100,000 | ||
Energy And Risk Operations Related Foreign Currency Contracts [Member] | |||||
| Notional amount of foreign currency derivative sale contracts | 17,100,000 | 17,100,000 | 10,000,000 | ||
| Notional amount of foreign currency derivative purchase contracts | 75,000,000 | 75,000,000 | 0 | ||
| Guarantees | 368,400,000 | 368,400,000 | |||
Investment Portfolio Related Foreign Currency Forward Contracts [Member] | |||||
| Notional amount of foreign currency derivative sale contracts | 350,200,000 | 350,200,000 | 281,000,000 | ||
| Notional amount of foreign currency derivative purchase contracts | 166,400,000 | 166,400,000 | 69,200,000 | ||
Underwriting Operations Related Foreign Currency Contracts [Member] | |||||
| Notional amount of foreign currency derivative sale contracts | 694,200,000 | 694,200,000 | 188,100,000 | ||
| Notional amount of foreign currency derivative purchase contracts | 123,700,000 | 123,700,000 | 42,000,000 | ||
Credit Risk Contract [Member] | |||||
| Notional amount of credit risk derivative purchase contracts | 15,000,000 | 15,000,000 | 15,000,000 | ||
| Notional amount of credit risk derivative sale contracts | 79,000,000 | 79,000,000 | 118,000,000 | ||
Derivative Assets [Member] | |||||
| Energy and weather related derivatives at fair value, assets | 28,000,000 | 28,000,000 | 21,700,000 | ||
| Energy and weather related derivatives at fair value, liabilities | 4,200,000 | 4,200,000 | 3,700,000 | ||
Derivative Liabilities [Member] | |||||
| Energy and weather related derivatives at fair value, assets | 10,800,000 | 10,800,000 | 9,900,000 | ||
| Energy and weather related derivatives at fair value, liabilities | $ 32,100,000 | $ 32,100,000 | $ 24,900,000 | ||