Stock Plans (Tables)

6 Months Ended

Jun. 30, 2019

Share-based Payment Arrangement [Abstract]

Disclosure of share-based compensation arrangements by payment award

During the six months ended June 30, 2019 and 2018, shares granted to eligible employees and the grant date fair value per share related to PSU awards were as follows:

	Number of Shares Granted	PSU Grant Date Fair Value Subject to Other Performance Factors Per Share		PSU Grant Date Fair Value Subject to TSR Performance Factor Per Share
2019	625,200		$ 77.20		$ 83.59
2018	401,500		$ 100.69		$ 118.98

Compensation expense related to PSU awards was as follows:

	Compensation Expense Related to PSU Awards
(in millions)	For the Six Months Ended June 30,		For the Three Months Ended June 30,
2019		$ 33		$ 15
2018		$ 30		$ 9

During the six months ended June 30, 2019 and 2018, shares granted to eligible employees and the weighted-average grant date fair value per share related to RSU awards were as follows:

	Number of Shares Granted	Weighted-Average Grant Date Fair Value Per RSU Award Granted
2019	1,643,780		$ 77.18
2018	1,257,380		$ 100.70

Compensation expense related to RSU awards was as follows:

	Compensation Expense Related to RSU Awards
(in millions)	For the Six Months Ended June 30,		For the Three Months Ended June 30,
2019		$ 64		$ 28
2018		$ 63		$ 25

Schedule of assumptions used to determine the grant date fair value of the PSU awards subject to the TSR performance factor

The following assumptions were used to determine the grant date fair value of the PSU awards subject to the TSR performance factor:

	2019			2018
Risk-free interest rate (a)	2.4	%		2.3	%
Expected volatility	21.4	%	(b)	19.6	%	(c)

^(a) Based on the U.S. Treasury yield curve.

^(b) Determined using the observed historical volatility.

^(c) Determined using a weighted-average of historical and implied volatility.