Litigation and contingencies (Details) (USD $)	6 Months Ended
	Jun. 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 named as defendants in complaint	2
Number of C-BASS officers named as defendants in complaint	2
Countrywide dispute [Abstract]
Minimum number of loans, filing date of action	1,400
Minimum number of loans, filing date of amended demand in the arbitration proceeding	3,300
Minimum number of bulk insurance policies	30
Minimum number of loans by plaintiff as of April 2011	5,000
Minimum amount of damages sought	150,000,000
Number of loans that each of the plaintiff and the defendant have seleccted	12
Number of members on arbitration panel	3
Total number of loans selected by both plaintiff and defendant combined	24
Mitigation of paid losses	375,000,000
Average claims payment had the loans not been rescinded (per loan)	71,400
Number of loans in primary delinquency inventory related to plaintiff	40,219
Percentage of loans in primary delinquency inventory related to plaintiff (in hundredth)	22.00%
Claims paid (in hundredths)	75.00%
Claims rescinded (in hundredths)	25.00%
Mitigation of incurred losses Since January 2008	3,100,000,000
Mitigation on paid losses, excluding deductible amounts	2,400,000,000
Total loss reserves, estimated benefit from rescissions	900,000,000
Freddie Mac dispute [Abstract]
Difference in aggregate loss limit under pool insurance policy	535,000,000
Impact of aggregate loss limit difference under pool insurance policy on results of operations	$ 52,000,000