Pensions and Other Postretirement Benefits Pensions and Other Postretirement Benefits - Defined Contribution Plans (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Compensation and Retirement Disclosure [Abstract]
Defined contribution plan, total cost recognized	$ 31	$ 30	$ 30
Defined contribution plan and other non-qualified supplemental retirement plan, total expense recognized (less than $3 million)	$ 3	$ 3	$ 3