Guarantees and Contingent Liabilities (Details) (USD $)		3 Months Ended
	Dec. 31, 2011 ELNY	Mar. 31, 2013 Obligations of insolvent insurance companies ELNY	Mar. 31, 2013 Guarantee on fixed income securities
Guarantees and Contingent Liabilities
Current publicly available estimated shortfall from the Bureau		$ 1,570,000,000
Aggregate limit on insurer assessments		558,000,000
Amount used out of limit on insurer assessments		40,000,000
Three-year average market share for New York (as a percent)	1.20%
Accrued liability for estimated aggregate exposure, net of taxes		10,000,000
Pre-tax liability for guaranty fund assessments		16,000,000
Pre-tax liability for participation in an industry sponsored plan		3,000,000
Maximum amount at risk pursuant to a guarantee			$ 4,000,000