Stock-Based Compensation - Stock option activity (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	12 Months Ended
	Dec. 31, 2016		Dec. 31, 2015	Dec. 31, 2014
Options
Outstanding at beginning of period, Options	130		130	129
Granted, Options	0		0	1
Forfeited, Options	(16)		0	0
Outstanding at end of period, Options	114	[1]	130	130
Weighted Average Exercise Price
Outstanding at beginning of period, Weighted Average Exercise Price	$ 218.46		$ 218.46	$ 218.38
Granted, Weighted Average Exercise Price	0.00		0.00	229.84
Forfeited, Weighted Average Exercise Price	227.19		0.00	0.00
Outstanding at end of period, Weighted Average Exercise Price	$ 217.24	[1]	$ 218.46	$ 218.46
Stock option activity, additional disclosure
Options exercisable at end of period, Options	85	[2]	93	88
Options exercisable at end of period, Weighted Average Exercise Price	$ 203.48	[2]	$ 202.48	$ 199.50
Available for grant at end of period	26		10	10
Stock options outstanding, weighted average remaining contractual term	2 years 3 months 18 days
Stock options outstanding, intrinsic value	$ 0.0
Exercisable stock options, weighted average remaining contractual term	1 year 3 months 6 days
Stock options exercisable, intrinsic value	$ 0.0

[1] Stock options outstanding at December 31, 2016 have a weighted average remaining contractual term of 2.3 years and there is no intrinsic value.

[2] Exercisable stock options at December 31, 2016 have a weighted average remaining contractual term of 1.3 years and there is no intrinsic value.