Litigation and contingencies (Details) (USD $)	9 Months Ended
	Sep. 30, 2011
Class action complaint under RESPA [Abstract]
Mortgage insurers named as defendants in class action	6
Discrimination complaint - U.S. Department of Housing and Urban Development [Abstract]
Number of employees named in an administrative action	2
Amount of aggregate fines related to the administrative action	$ 48,000
Class action complaints - Fulton County Employees' Retirement System [Abstract]
Number of previously filed purported class action complaints	5
Number of officers of C-BASS named as defendants in complaint	2
Number of officers named as defendants in amended complaint	2
Number of officers of C-BASS named as defendants in amended complaint	2
Countrywide dispute [Abstract]
Mitigation of paid losses	400,000,000
Average claims payment had the loans not been rescinded (per loan)	71,500
Amount of damages sought	700,000,000
Number of loans that each of the plaintiff and the defendant have selected	12
Number of members on arbitration panel	3
Total number of loans selected by both plaintiff and defendant combined	24
Number of loans in primary delinquency inventory related to plaintiff	38,099
Percentage of loans in primary delinquency inventory related to plaintiff (in hundredth)	21.00%
Claims paid (in hundredths)	77.00%
Claims rescinded (in hundredths)	23.00%
Mitigation of incurred losses since January 2008	3,100,000,000
Mitigation on paid losses, excluding deductible amounts	2,500,000,000
Amount excluded from mitigation on paid losses that would have been applied to a deductible	600,000,000
Total loss reserves, estimated benefit from rescissions	800,000,000
Freddie Mac dispute [Abstract]
Impact of aggregate loss limit difference under pool insurance policy on results of operations	126,000,000
Difference in aggregate loss limit under pool insurance policy	$ 535,000,000