New Accounting Standards (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Diluted weighted average shares outstanding	122,747,848	127,439,641	123,035,779	128,018,729
New Accounting Pronouncement, Early Adoption, Effect [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Excess tax benefits	$ 5		$ 7
Diluted weighted average shares outstanding	122,700,000		123,000,000
Increase in earnings per share as a result of the adoption (in dollars per share)	$ 0.03		$ 0.04
Excess tax benefit from stock option exercises			$ 7
Previous Accounting Guidance [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Excess tax benefits		$ 6		$ 11
Diluted weighted average shares outstanding	121,900,000		122,300,000