Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2017

Stock option activity for the year ended December 31, 2017 was as follows:

	Shares Subject to Options			Weighted Average Option Price		Weighted Average Remaining Contractual Term (Yrs)		Aggregate Intrinsic Value (in millions) (b)
Outstanding at December 31, 2016		4,625,678		$	18.73
Granted		180,677			27.97
Exercised		(1,263,767	)		16.17
Forfeited/Expired		(306,915	)		19.54

Outstanding at December 31, 2017		3,235,673		$	20.16		6.3	$	45.8


Exercisable at December 31, 2017		1,786,898		$	18.31		5.4	$	28.6


Exercisable and expected to vest at
December 31, 2017 (a)		3,138,460		$	20.09		6.3	$	44.6


(a)	In addition to the options that are vested at December 31, 2017, the Company expects a portion of the unvested options to vest in the future. Options expected to vest in the future are determined by applying an estimated forfeiture rate to the options that are unvested as of December 31, 2017.
(b)	The aggregate intrinsic value is based on the positive difference between the fair value of the Company's common stock price of $34.32 on December 31, 2017, or the date of exercises, as appropriate, and the exercise price of the underlying stock options.

The following table summarizes information about restricted stock award activity during the year ended December 31, 2017:

	Shares Subject to Restriction			Weighted Average Grant Date Fair Value
Outstanding at December 31, 2016		172,506		$	19.37
Vested		(82,924	)		18.17
Forfeited		(4,053	)		22.46

Outstanding at December 31, 2017		85,529		$	20.39

The following table summarizes information about restricted stock unit activity for year ended December 31, 2017:

	Shares Subject to Restriction			Weighted Average Grant Date Fair Value
Outstanding at December 31, 2016		262,317		$	22.32
Granted		488,552			26.55
Vested		(67,057	)		22.27
Forfeited		(31,689	)		22.81

Outstanding at December 31, 2017		652,123		$	25.47