Share-Based Compensation - Schedule of Additional Information on Restricted Stock Units (Details) - Restricted Stock Units (RSUs) [member] - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Schedule Of Additional Information On Restricted Stock Units [Line Items]
Number of shares granted	1,169,238	679,546	1,883,454
Weighted average grant date fair value per share	$ 59.73	$ 82.38	$ 64.59
Fair value of shares vested (in millions)	$ 40	$ 90	$ 0	[1]

[1] The fair value of shares vested during the year ended December 31, 2014 was less than $1 million.