Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2017

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

The following table summarizes the changes in the number of shares of common stock under option for 2017 (shares and aggregate intrinsic value in millions):


	Shares			Weighted- Average Exercise Price Per Share		Weighted Average Remaining Life (years)		Aggregate Intrinsic Value
Outstanding at December 31, 2016		0.7		$	20
Exercised		(0.3	)	$	25

Outstanding at December 31, 2017 (a)		0.4		$	16		2.4	$	6.3

(a)	All options outstanding are exercisable

Summary of Changes of Restricted Stock and Restricted Stock Units

The following table summarizes the changes in the number of outstanding restricted stock units for 2017 (shares in millions):


	Restricted Stock Units			Weighted-Average Grant Date Fair Value Per Share -
Outstanding at December 31, 2016		4.3		$	48
Granted		2.0			47
Grant Adjustments (b)		0.1			39
Vested		(1.4	)		40
Forfeited		(0.6	)		48

Outstanding at December 31, 2017		4.4			50

Expected to vest at December 31, 2017		2.1			47

(b)	Represents the incremental shares issued from the shares originally granted which were dependent upon the achievement of specified performance criteria.

Summary of Total Unrecognized Compensation Cost Related to Stock-based Compensation

The following table summarizes the Company’s total unrecognized compensation cost related to stock-based compensation as of December 31, 2017 (in millions):


	Unrecognized Compensation Cost		Weighted-Average Period of Expense Recognition (in years)
Restricted stock units	$	87.9		1