Stock-Based Compensation Plans - Balance Sheet Classification of Obligations related to Outstanding Performance Share Awards Not Yet Settled (Details) - USD ($) $ in Millions		Dec. 31, 2015	Dec. 31, 2014
Common Stock [Abstract]
Current liabilities	[1]	$ 28	$ 28
Deferred credits and other liabilities	[2]	32	36
Common stock		35	33
Total		$ 95	$ 97

[1] Represents the current liability related to performance share awards expected to be settled in cash.

[2] Represents the long-term liability related to performance share awards expected to be settled in cash.