Share-Based Compensation Plans (Tables)

12 Months Ended

Dec. 31, 2018

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

Summary of stock option activity

A summary of stock option activity is as follows:

	Shares (000)		Wtd. Avg.  Exercise Price  Per Share		Wtd. Avg.  Remaining  Contractual Term (years)	Aggregate Intrinsic Value (in millions)
Outstanding, January 1, 2016	1,272			$64
Granted	166		75
Exercised	(279	)	63				$5
Expired or cancelled	(32	)	67
Outstanding, December 31, 2016	1,127			$66	4.9		$26
Vested or expected to vest, December 31, 2016	1,122			$66	4.9
Exercisable, December 31, 2016	756			$62	3.3		$20
Outstanding, January 1, 2017	1,127			$66
Granted	145		97
Exercised	(680	)	64				$24
Expired or cancelled	(18	)	75
Outstanding, December 31, 2017	574			$77	7.1		$28
Vested or expected to vest, December 31, 2017	571			$77	7.1
Exercisable, December 31, 2017	220			$65	5.3		$14
Outstanding, January 1, 2018	574			$77
Granted	122		123
Exercised	(24	)	78				$1
Expired or cancelled	—		—
Outstanding, December 31, 2018	672			$85	5.9		$1
Vested or expected to vest, December 31, 2018	670			$85	5.9
Exercisable, December 31, 2018	401			$76	4.5		$1

Schedule of options outstanding and exercisable

Options outstanding and exercisable as of December 31, 2018 were as follows:

	Options Outstanding				Options Exercisable
Exercise Price	Shares (000)	Weighted- Average  Remaining  Contractual Life (years)	Weighted- Average  Exercise Price		Shares (000)	Weighted-Average  Exercise Price
$27-$49	35	1.8		$39	35		$39
$50-$73	67	2.8	55		67	55
$74-$85	309	5.8	77		223	77
$86-$123	261	7.4	109		76	105
	672	5.9		$85	401		$76

Assumptions used to estimate fair value of share awards

We estimated the fair value of each stock option on the date of grant using the Black-Scholes option pricing model and the following assumptions:

Year Ended December 31	2018		2017		2016
Average risk-free interest rate	2.6	%	2.0	%	1.4	%
Expected dividend yield	1.6	%	2.0	%	2.1	%
Expected volatility	27.0	%	31.0	%	33.0	%
Expected term (years)	6.0		6.0		6.0

Summary of restricted stock activity

A summary of restricted stock activity is as follows:

	Shares (000)		Wtd. Avg. Price Per Share		Wtd. Avg. Remaining  Contractual  Term (years)	Aggregate  Intrinsic Value (in millions)
Unvested, January 1, 2016	405			$64	1.3
Granted	232		75
Vested	(172	)	62
Forfeited	(14	)	76
Unvested, December 31, 2016	451			$70	1.4
Granted	167			$98
Vested	(133	)	79
Forfeited	(37	)	80
Unvested, December 31, 2017	448			$77	1.2
Granted	145			$119
Vested	(174	)	77
Forfeited	(23	)	89
Unvested, December 31, 2018	396			$92	1.3		$26

Summary of performance share units detail by grant year

A summary of the performance share units detail by grant year is as follows:

	2015	2016	2017	2018
Grant Date(s)	February 11, 2015	February 16, 2016	February 9, 2017	February 15, 2018
Performance Period (years)	2015-2017	2016-2018	2017-2019	2018-2020
Vesting Date	February 2018	February 2019(a)	February 2020(a)	February 2021(a)
Payout Levels (in units):
Threshold Award	82,298	65,141	57,563	47,003
Target Award	164,595	130,282	115,125	94,005
Outstanding Award	329,190	260,564	230,250	188,010
Shares Issued in 2018	219,519	—	—	—
Payout Achieved Over Performance Period	—	123,767	—	—

(a) 2016, 2017 and 2018 awards are scheduled to vest in February 2019, 2020, and 2021, respectively, when the Executive Compensation and Human Resources Committee of the Board of Directors determines the achievement of the performance criteria.