Income Taxes - Additional Information (Details) (USD $)	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Jul. 31, 2013
Income tax expense	$ 31,000,000	$ 34,000,000
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent	35.00%	35.00%
Effective Income Tax Rate Reconciliation, Percent	30.00%	48.00%
Effective Income Tax Rate Reconciliation, Repatriation of Foreign Earnings, Amount	1,000,000	1,000,000
Effective Income Tax Rate Reconciliation, Other Adjustments, Amount		4,000,000
Deferred tax asset valuation allowance reasonably likely to reverse in next twelve months	500,000,000
Senior Notes Sold In 2013 [Member]
Senior notes issued			$ 750,000,000