Fair Value Measurements (Details) (USD $)	6 Months Ended
	Jun. 30, 2011
200 basis point increase | Maiden Lane III
Variable Interest Entity
Fair Value Change	(632,000,000)
200 basis point decrease | Maiden Lane III
Variable Interest Entity
Fair Value Change	717,000,000
400 basis point increase | Maiden Lane III
Variable Interest Entity
Fair Value Change	(1,192,000,000)
400 basis point decrease | Maiden Lane III
Variable Interest Entity
Fair Value Change	1,533,000,000
10% increase | Maiden Lane III
Variable Interest Entity
Fair Value Change	790,000,000
10% decrease | Maiden Lane III
Variable Interest Entity
Fair Value Change	(805,000,000)
20% increase | Maiden Lane III
Variable Interest Entity
Fair Value Change	1,564,000,000
20% decrease | Maiden Lane III
Variable Interest Entity
Fair Value Change	(1,619,000,000)
Maiden Lane II
Variable Interest Entity
Fair Value Change	170,000,000
Maiden Lane, transaction price	1,000,000,000
Maiden Lane II | Federal Reserve Bank of New York (FRBNY)
Variable Interest Entity
Percentage change in the liquidation proceeds resulting in change in fair value (as a percent)	10.00%
Maiden Lane III
Variable Interest Entity
Fair Value Change	513,000,000
Maiden Lane, transaction price	5,000,000,000