Equity-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2017

Restricted Stock Units — A summary of our RSUs is presented in the table below (units in thousands):


		Weighted Average
		Per Share
	Units	Fair Value
Unvested as of January 1, 2017	490	$	51.32
Granted	138	$	73.67
Vested	(169)	$	42.65
Forfeited	(15)	$	61.62
Unvested as of December 31, 2017	444	$	61.20

Summary of PSUs

A summary of our PSUs, at 100% of the targeted amount, is presented in the table below (units in thousands):


		Weighted Average
		Per Share
	Units	Fair Value
Unvested as of January 1, 2017	1,505	$	68.98
Granted	400	$	84.54
Vested	(570)	$	55.22
Forfeited	(36)	$	85.57
Unvested as of December 31, 2017	1,299	$	84.78

Summary of Stock Options

A summary of our stock options is presented in the table below (options in thousands):


		Weighted Average
		Per Share
	Options	Exercise Price
Outstanding as of January 1, 2017	5,643	$	45.12
Granted	1,732	$	65.45
Exercised	(2,331)	$	42.19
Forfeited or expired	(159)	$	53.35
Outstanding as of December 31, 2017 (a)	4,885	$	53.46
Exercisable as of December 31, 2017 (b)	2,124	$	41.56

(a)

Stock options outstanding as of December 31, 2017 have a weighted average remaining contractual term of 6.5 years and an aggregate intrinsic value of $160 million based on the market value of our common stock on December 31, 2017.

(b)

Stock options exercisable as of December 31, 2017 have an aggregate intrinsic value of $95 million based on the market value of our common stock on December 31, 2017.

Summary of Exercisable Stock Options

Stock options exercisable as of December 31, 2017 were as follows (options in thousands):


		Weighted Average
		Per Share		Weighted Average
Range of Exercise Prices	Options	Exercise Price		Remaining Years
$32.315-$40.00	1,127	$	36.13	3.6
$40.01-$50.00	541	$	41.37	6.2
$50.01-$56.235	456	$	55.21	7.5
$32.315-$56.235	2,124	$	41.56	5.1

Weighted Average Assumptions Used to Value Employee Stock Options Granted

The following table presents the weighted average assumptions used to value employee stock options granted during the years ended December 31 under the Black-Scholes valuation model:


	2017		2016		2015
Expected option life	3.5	years	4.7	years	4.4	years
Expected volatility	15.3	%	18.4	%	16.7	%
Expected dividend yield	2.3	%	2.9	%	2.8	%
Risk-free interest rate	1.7	%	1.3	%	1.4	%