Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2017

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

Summary of Stock Based Compensation Activity Related to Nonvested RSUs

The following table summarizes activity related to nonvested RSUs:

	Number of RSUs (In thousands)		Weighted Average Grant-Date Fair Value Per Share
Nonvested at December 31, 2014	2,326		$	97.80
Granted	595		192.47
Vested	(1,642	)	103.30
Forfeited	(43	)	132.28
Nonvested at December 31, 2015	1,236		$	134.87
Granted	679		206.69
Vested	(1,009	)	137.62
Forfeited	(118	)	203.65
Nonvested at December 31, 2016	788		$	183.00
Granted	519		254.58
Vested	(624	)	201.65
Forfeited	(32	)	223.23
Nonvested at December 31, 2017	651		$	220.21

Stock Options

The following table pertains to stock options granted through 2012, in addition to stock options that vested and were exercised in 2017, 2016 and 2015 (in millions):

	2017		2016		2015
Grant-date fair value of all stock options that vested	$	—	$	—	$	8
Intrinsic value of all stock options exercised	139		172		265