Share-Based Compensation (Tables)

6 Months Ended

Jun. 30, 2019

Equity [Abstract]

Summary of Stock Options

The following is a summary of stock option activity for the six months ended June 30, 2019:

	Number of Options (in thousands)		Weighted Average Exercise Price per Option
Outstanding at December 31, 2018	3,610		$	46.44
Granted	493		76.16
Exercised	(448	)	38.62
Outstanding at June 30, 2019	3,655		51.41

Details of Stock Options Outstanding

Details of stock options outstanding as of June 30, 2019 are as follows:

	Number of Options (in thousands)	Weighted Average Exercise Price		Weighted Average Remaining Contractual Life (Years)	Aggregate Intrinsic Value (In millions)
Vested or expected to vest	3,655	$	51.41	6.6	$	126
Exercisable	2,581	$	43.97	5.6	$	108

Stock Options Valuation Assumptions

During the six months ended June 30, 2019 and 2018, we used the weighted-average assumptions in the table below to compute the value of all options for shares of common stock granted to employees:

	Six Months Ended June 30,
Assumptions:	2019			2018
Risk-free interest rate	2.49		%	2.66		%
Expected life in years	5.9			6.0
Expected volatility	20		%	20		%
Expected dividend yield	1.44		%	1.43		%
Estimated weighted-average fair value of options granted per share	$	15.45		$	13.98

Summary of Nonvested Restricted Stock Options

The following is a summary of the non-vested restricted share activity for the six months ended June 30, 2019:  

	Number of Restricted Shares (in thousands)	Weighted Average Grant-Date Fair Value per Share
Non-vested at December 31, 2018	4,470	$	60.56
Granted	1,656	76.46
Vested	(2,123)	57.57
Forfeited	(143)	66.28
Non-vested at June 30, 2019	3,860	68.81