Share-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2015

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Summary of stock options outstanding and stock option activity

A summary of stock options outstanding as of December 31, 2015 and of stock option activity during 2015 is presented below:

	Number of Options (000)		Weighted Average Exercise Price		Weighted Average Remaining Contractual Term (years)	Aggregate Intrinsic Value (millions)
Outstanding at January 1, 2015	3,982		$	26.77	4.17	$	31
Exercised	(410	)	14.61
Canceled	(67	)	41.50
Forfeited	(9	)	14.76
Outstanding at December 31, 2015	3,496		$	28.00	3.06	$	19
Exercisable at December 31, 2015	3,363		$	28.51	2.93	$	18
Vested or expected to vest at December 31, 2015	3,496		$	28.00	2.99	$	19

Schedule of MSUs valuation assumptions

We estimated the fair value of each MSU granted on the date of grant using a Monte Carlo simulation that used the assumptions noted in the following table. Volatility was based on stock price history immediately prior to grant for a period commensurate with the expected term. The risk-free rate was based on zero-coupon U.S. government issues at the time of grant. The expected term represents the period from the valuation date to the end of the performance period.

Assumptions:	2015		2014		2013
Expected volatility	42.70	%	54.93	%	60.97	%
Risk-free rate	1.09	%	0.63	%	0.35	%
Expected term (in years)	2.95		2.94		2.38
Expected dividends	—		—		—

Schedule of nonvested MSUs outstanding and activity

Nonvested MSUs outstanding as of December 31, 2015 and MSU activity during 2015 were as follows:

	Weighted Number of Shares (000)		Weighted Average Grant Date Fair Value
Nonvested at January 1, 2015	511		$	38.43
Granted	474		30.06
Vested	(156	)	34.80
Forfeited	(86	)	34.34
Nonvested at December 31, 2015	743		34.33

Summary of nonvested RSUs outstanding and activity

RSUs outstanding as of December 31, 2015 and RSU activity during 2015 were as follows:

	Number of Shares (000)		Weighted Average Grant Date Fair Value
Nonvested at January 1, 2015	423		$	20.12
Granted	94		28.56
Vested	(220	)	17.84
Forfeited	(27	)	24.36
Nonvested at December 31, 2015	270		24.49

Schedule of performance based units valuation assumptions

We estimated the fair value of each performance share granted on the date of grant using a Monte Carlo simulation that uses the assumptions noted in the following table. Volatility was based on stock price history immediately prior to grant for a period commensurate with the expected term. The risk-free rate was based on zero coupon U.S. government issues at the time of grant. The expected term represents the period from the grant date to the end of the three-year performance period.

Assumptions:	2015		2014		2013
Expected volatility	42.70	%	54.93	%	59.98	%
Risk-free rate	1.09	%	0.63	%	0.43	%
Expected term (in years)	2.95		2.94		2.88
Expected dividends	—		—		—

Summary of nonvested performance share outstanding and performance share activity

Nonvested performance shares outstanding as of December 31, 2015 and performance share activity during 2015 were as follows:

	Weighted Number of Shares (000)		Weighted Average Grant Date Fair Value
Nonvested at January 1, 2015	203		$	42.82
Granted	147		30.63
Vested	(89	)	38.89
Forfeited	(39	)	24.12
Nonvested at December 31, 2015	222		37.20