Variable Interest Entities - Securitization Activity (Details 4) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Variable Interest Entity (VIE) or Potential VIE, Information Unavailability [Member] | Residential Mortgage [Member]
Securitization activity [Abstract]
Principal securitized	$ 443,000,000	$ 0	$ 1,059,000,000	$ 0
All cash flows during the period:
Proceeds from new securitizations	446,000,000	0	1,080,000,000	0
Servicing fees collected	158,000,000	171,000,000	285,000,000	351,000,000
Purchases of previously transferred financial assets (or the underlying collateral)	19,000,000	52,000,000	271,000,000	111,000,000
Cash flows received on interests	30,000,000	55,000,000	55,000,000	108,000,000
Variable Interest Entity (VIE) or Potential VIE, Information Unavailability [Member] | Commercial Mortgage Backed Securities
Securitization activity [Abstract]
Principal securitized	3,078,000,000	2,063,000,000	5,284,000,000	2,063,000,000
All cash flows during the period:
Proceeds from new securitizations	3,149,000,000	2,161,000,000	5,426,000,000	2,161,000,000
Servicing fees collected	2,000,000	1,000,000	3,000,000	2,000,000
Purchases of previously transferred financial assets (or the underlying collateral)	0	0	0	0
Cash flows received on interests	78,000,000	40,000,000	142,000,000	64,000,000
Fair Value, Inputs, Level 2 [Member] | Commercial Mortgage Backed Securities
All cash flows during the period:
Proceeds from new securitizations	3,100,000,000	2,200,000,000	5,200,000,000	2,200,000,000
Fair Value, Inputs, Level 2 [Member] | Commercial Mortgage [Member]
All cash flows during the period:
Proceeds from new securitizations	0		207,000,000
Fair Value, Inputs, Level 2 [Member] | Residential and commercial mortgage securitizations
All cash flows during the period:
Proceeds from new securitizations	$ 446,000,000		$ 1,100,000,000