- Income Taxes (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		12 Months Ended	3 Months Ended									12 Months Ended	3 Months Ended	12 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013	Mar. 31, 2014 United States	Mar. 31, 2013 United States	Mar. 31, 2014 Bermuda	Mar. 31, 2013 Bermuda	Mar. 31, 2014 UK	Mar. 31, 2013 UK	Mar. 31, 2014 UK April 1, 2014 to April 1, 2015 [Member]	Mar. 31, 2014 UK Subsequent to April 1, 2015 [Member]	Mar. 31, 2014 UK Subsequent to April 1, 2013	Mar. 31, 2014 UK April 1, 2012 to April 1, 2013 [Member]	Mar. 31, 2013 UK Prior to April 1, 2012	Mar. 31, 2013 UK Prior to April 1, 2012
Pretax Income and Revenue by Tax Jurisdiction
Realization assessment period	3 years
Federal statutory income tax rate (as a percent)				35.00%				23.00%		21.00%	20.00%	21.00%	23.00%		24.00%
Value added tax rate								20.00%
Effective Tax Rate Reconciliation
Expected tax provision (benefit) at statutory rates in taxable jurisdictions	$ 38	$ (48)
Tax-exempt interest	(14)	(14)
Change in liability for uncertain tax positions	1	(8)
Other	2	2
Total provision (benefit) for income taxes	27	(68)
Effective tax rate (as a percent)	38.80%	31.80%						21.50%						23.25%
Income (loss) before provision for income taxes	69	(212)		113	(134)	(37)	(78)	(7)	0
Revenue	195	(176)		195	(127)	1	(49)	(1)	0
Accrued interest and penalties, uncertain tax positions	0.3	1.0
Unrecognized Tax Benefits, Decrease Resulting from Settlements with Taxing Authorities			(9)
Interest and penalties accrued	3		3
Unrecognized tax benefits that would affect the effective tax rate, if recognized	$ 21		$ 20