Litigation and Contingencies (Details) - USD ($) $ in Millions	6 Months Ended	9 Months Ended	12 Months Ended
	Jun. 30, 2009	Sep. 30, 2016	Dec. 31, 2015
Curtailments [Abstract]
Average paid claim reduction due to curtailments (in hundredths)		5.40%	6.70%
Claims resolved by rescissions [Abstract]
Percentage of claims received in a quarter resolved by rescission, lower range limit (in hundredths)		4.00%
Percentage of claims received in a quarter resolved by rescission, upper range limit (in hundredths)	28.00%
Maximum exposure associated with other discussions and legal proceedings		$ 281
Other Legal Proceedings [Abstract]
Underwriting remedy expense			$ 1