Subsequent Events - Narratives (Details) (USD $)	3 Months Ended								12 Months Ended				1 Months Ended		1 Months Ended	12 Months Ended		1 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2012 Subsequent Events [Member] Repurchase Request Resolution Agreement [Member]	Jan. 31, 2013 Bank of America [Member] Subsequent Events [Member] Repurchase Request Resolution Agreement [Member] contracts	Dec. 31, 2012 Bank of America [Member] Subsequent Events [Member] Repurchase Request Resolution Agreement [Member]	Jan. 31, 2013 Bank of America [Member] Subsequent Events [Member] Compensatory Fee Resolution Agreement [Member]	Dec. 31, 2012 Bank of America [Member] Subsequent Events [Member] Compensatory Fee Resolution Agreement [Member]	Dec. 31, 2012 Unpaid Principal Balance [Member] Bank of America [Member] Subsequent Events [Member] Repurchase Request Resolution Agreement [Member]	Jan. 31, 2013 Repurchase Request [Member] Bank of America [Member] Subsequent Events [Member] Repurchase Request Resolution Agreement [Member]	Jan. 31, 2013 Mortgage Insurance Claims [Member] Bank of America [Member] Subsequent Events [Member] Repurchase Request Resolution Agreement [Member]	Dec. 31, 2012 Repurchase Request Outstanding [Member] Unpaid Principal Balance [Member] Bank of America [Member]
Subsequent Events [Line Items]
Cash payment made to Fannie Mae																		$ 3,600,000,000	$ 518,000,000
Number of loans repurchased from Fannie Mae													29,500
Gross proceeds from loans repurchased from Fannie Mae													6,600,000,000
Mortgage repurchase requests outstanding														11,300,000,000
Percentage of repurchase requests outstanding																	97.00%			73.00%
Initial payment of compensatory fees															1,300,000,000
Foreclosed property (income) expense	$ (475,000,000)	$ (48,000,000)	$ (70,000,000)	$ 339,000,000	$ 37,000,000	$ 733,000,000	$ (478,000,000)	$ 488,000,000	$ (254,000,000)	$ 780,000,000	$ 1,718,000,000	$ (106,000,000)				$ (203,000,000)