Equity Compensation Plans (Tables)

3 Months Ended

Mar. 31, 2020

Share-based Payment Arrangement [Abstract]

Summary of Stock Options Outstanding

A summary of the status of the stock options, restricted stock, and PSUs awarded under the 2013 Incentive Plan as of December 31, 2019 and March 31, 2020 and changes during the interim period are presented below:

	Stock Option						Restricted Stock				PSU
	Number of Options		Weighted Average Exercise Price		Aggregate Intrinsic Value		Number of Shares		Weighted Average Grant Date Fair Value Per Share		Number of Shares		Weighted Average Grant Date Fair Value Per Share
					(in millions)
Outstanding at December 31, 2019	6,432,814		$	79.51	$	449.2	428,729		$	107.96	93,960		$	158.50
Granted	883,282		$	158.63			149,040		$	158.62	50,736		$	192.93
Dividend reinvestment	—		$	—			—		$	—	268			Not applicable
Exercised or lapsed	(449,007	)	$	43.28	$	50.7	(2,478	)	$	107.87	—
Canceled, expired or forfeited	(49,672	)	$	113.26			(8,842	)	$	118.60	—
Outstanding at March 31, 2020	6,817,417		$	91.86	$	324.0	566,449		$	121.00	144,964		$	170.40
Exercisable at March 31, 2020	3,808,076		$	66.94	$	275.9
Exercisable at December 31, 2019	4,175,855		$	65.05	$	352.0
Nonvested at March 31, 2020	3,008,420						566,449				145,121
Expected to vest at March 31, 2020	2,604,017						487,007				288,444	(1)

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Includes estimated performance achievement

Valuation Assumptions

The fair value of the stock options granted for the three months ended March 31, 2020 was estimated using a Black-Scholes valuation model that uses the weighted average assumptions noted in the following table. There were no stock options granted for the three months ended March 31, 2019.

	2020
Option pricing model		Black-Scholes
Expected volatility		18.17	%
Risk-free interest rate		1.59	%
Expected term in years		4.3
Dividend yield		0.71	%
Weighted average grant date fair value per stock option	$	25.49