Income Taxes - Narrative (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended	12 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Dec. 31, 2013	Dec. 31, 2013	Mar. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Operating Loss Carryforwards [Line Items]
Effective income tax rate reconciliation US income tax rate (as a percent)				35.00%
U.K. marginal corporate tax rate (as a percent)	26.00%	28.00%	23.00%	23.25%	24.00%	24.50%	26.50%
Foreign tax credit			$ 37	$ 37		$ 30
Alternative minimum tax credit			90	90		58
Tax credit carryforward foreign acquired in business combination transaction			22	22
Realization assessment period for which cumulative operating income considered				3 years
Interest and penalties related to uncertain tax positions				1		1	1
Accrued interest and penalties, uncertain tax positions			3	3		3
Unrecognized tax benefits that would impact effective tax rate			20	20
Liability under tax allocation agreement			5	5		6
Reduction in liability for tax basis step-up adjustment				1
AGRO
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards			$ 13	$ 13		$ 20
United Kingdom
Operating Loss Carryforwards [Line Items]
Corporate tax rate				23.00%
Value added tax rate				20.00%
April 1, 2014 to April 1, 2015 | United Kingdom
Operating Loss Carryforwards [Line Items]
Corporate tax rate				21.00%
Subsequent to April 1, 2015 | United Kingdom
Operating Loss Carryforwards [Line Items]
Corporate tax rate				20.00%