Share-based Payments (Tables)

12 Months Ended

Dec. 31, 2018

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

Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions

Assumptions used to calculate the fair value of stock options in each period are noted in the following table. Expected volatility is based on the simple average of implied and historical volatility using the daily closing prices of the Company’s stock for a period equal to the expected term of the option. The risk-free interest rate is based on the U.S. Treasury rate at the time of the grant for instruments of comparable life. There were no stock options granted or issued in 2018.



	Years Ended December 31,
	2017		2016
Weighted average assumptions used in option valuations:
Expected volatility	35.35	%	42.54	%
Expected dividend yield	1.97	%	3.86	%
Expected term (in years)	7		7
Risk-free interest rate	2.34	%	1.65	%

Schedule of Share-based Compensation, Stock Options, Activity

A summary of the status of our stock options as of December 31, 2018, and activity during 2018, is as follows:



	Shares (in millions)		Weighted Average Exercise Price		Weighted Average Remaining Contractual Term (Years)	Aggregate Intrinsic Value
Outstanding as of December 31, 2017	2.6		$	49.20
Granted	—		—
Cancelled	(0.2	)	$	91.88
Outstanding as of December 31, 2018	2.4		$	45.50	4.0	$	—
Exercisable as of December 31, 2018	2.0		$	48.60	3.4	$	—

Schedule of Share-based Compensation, Restricted Stock Units Award Activity

A summary of the status of our restricted stock units as of December 31, 2018, and activity during 2018, is as follows:



	Shares (in millions)		Weighted Average Grant Date Fair Value Per Share
Restricted stock units as of December 31, 2017	1.2		$	33.10
Granted	0.7		26.73
Issued and cancelled	(0.3	)	$	43.65
Restricted stock units as of December 31, 2018	1.6		$	27.27

Schedule Of Nonvested Performance Based Units Valuation Assumptions

A summary of the assumptions used to estimate the fair value of TSR performance units is as follows:



	Years Ended December 31,
	2018		2017		2016
Weighted average assumptions used in performance unit valuations:
Expected volatility	34.30	%	34.26	%	35.67	%
Expected dividend yield	0.37	%	1.97	%	3.86	%
Expected term (in years)	3		3		3
Risk-free interest rate	2.42	%	1.60	%	0.99	%

Schedule of Nonvested Performance-based Units Activity

A summary of our performance unit activity during 2018 is as follows:



	Shares (in millions)		Weighted Average Grant Date Fair Value Per Share
Outstanding as of December 31, 2017	1.1		$	33.26
Granted	0.4		28.09
Issued and cancelled	(0.2	)	$	43.79
Outstanding as of December 31, 2018	1.3		$	33.26