Stock Compensation - Additional Information (Details) - USD ($) shares in Millions, $ in Millions		3 Months Ended		9 Months Ended
	Mar. 31, 2015	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Cash received from exercise of stock options				$ 2
Cash paid to settle SARs and RSUs				2
Stock compensation expense		$ 6	$ 2	14	$ 11
Total unrecognized compensation cost related to nonvested awards granted and expected to vest		$ 22		$ 22
Weighted-average period in which the total unrecognized compensation cost is expected to be recognized	2 years
Performance Share Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term				3 years
Risk-free interest rate				0.89%
Dividend yield				0.98%
Expected volatility rate				33.90%
Historical volatility period				3 years
Stock Option And Stock Appreciation Rights [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options and SARs exercised in period				0.2
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares issued in period				0.4