Stock Based Awards and Other Equity Instruments (Tables)

6 Months Ended

Jun. 30, 2017

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Amount of Stock-Based Compensation Expense Related to Stock-Based Awards, Primarily Stock Options and Restricted Stock Units (RSUs)

The following table presents the amount of stock-based compensation expense related to stock-based awards, primarily stock options and restricted stock units (“RSUs”), on our unaudited condensed consolidated statements of operations during the periods presented:

	Three months ended						Six months ended
	June 30,						June 30,
	2017			2016			2017			2016
	(in millions)						(in millions)
Selling and marketing	$	6		$	5		$	11		$	10
Technology and content		13			11			20			21
General and administrative		9			7			16			12
Total stock-based compensation		28			23			47			43
Income tax benefit from stock-based compensation		(10	)		(8	)		(17	)		(15	)
Total stock-based compensation, net of tax effect	$	18		$	15		$	30		$	28

Summary of Stock Option Activity

The following table presents a summary of our stock option activity during the six months ended June 30, 2017:

				Weighted		Weighted
				Average		Average
				Exercise		Remaining		Aggregate
	Options			Price Per		Contractual		Intrinsic
	Outstanding			Share		Life		Value
	(in thousands)					(in years)		(in millions)
Options outstanding at December 31, 2016		5,818		$	57.60
Granted		1,502			42.88
Exercised (1)		(404	)		30.34
Cancelled or expired		(383	)		75.44
Options outstanding at June 30, 2017		6,533		$	54.89		6.7	$	6
Exercisable as of June 30, 2017		2,856		$	47.75		4.6	$	6
Vested and expected to vest after June 30, 2017 (2)		6,533		$	54.89		6.7	$	6

(1) Inclusive of 241,626 of options which were not converted into shares due to net share settlement in order to cover the aggregate exercise price and the required amount of employee withholding taxes. Potential shares that had been convertible under stock options that were withheld under net share settlement remain in the authorized but unissued pool under the 2011 Incentive Plan and can be reissued by the Company. Total payments for the employees’ tax obligations to the taxing authorities due to net share settlements are reflected as a financing activity within the unaudited condensed consolidated statements of cash flows.

(2) The Company accounts for forfeitures as they occur, rather than estimate expected forfeitures as allowed under GAAP and   therefore do not include a forfeiture rate in our vested and expected to vest calculation unless necessary for a performance condition award.

Weighted-Average Assumptions of Estimated Fair Value of Stock Option Grants

The fair value of stock option grants under the 2011 Incentive Plan has been estimated at the date of grant using the Black–Scholes option pricing model with the following weighted average assumptions for the periods presented:

	Three months ended						Six months ended
	June 30,						June 30,
	2017			2016			2017			2016
Risk free interest rate		1.87	%		1.08	%		1.91	%		1.20	%
Expected term (in years)		5.32			4.31			5.35			4.84
Expected volatility		40.93	%		42.09	%		41.52	%		41.82	%
Expected dividend yield	—  %			—  %			—  %			—  %

Summary of RSU Activity

The following table presents a summary of our RSU activity during the six months ended June 30, 2017:

				Weighted
				Average
				Grant-		Aggregate
	RSUs			Date Fair		Intrinsic
	Outstanding			Value Per Share		Value
	(in thousands)					(in millions)
Unvested RSUs outstanding as of December 31, 2016		2,856		$	69.35
Granted		4,002			42.88
Vested and released (1)		(791	)		67.73
Cancelled		(332	)		58.64
Unvested RSUs outstanding as of June 30, 2017		5,735		$	51.72	$	219
Expected to vest after June 30, 2017 (2)		5,735		$	51.72	$	219

(1) Inclusive of 231,022 RSUs withheld due to net share settlement to satisfy required employee tax withholding requirements. Potential shares which had been convertible under RSUs that were withheld under net share settlement remain in the authorized but unissued pool under the 2011 Incentive Plan and can be reissued by the Company. Total payments for the employees’ tax obligations to the taxing authorities due to net share settlements are reflected as a financing activity within the unaudited condensed consolidated statements of cash flows.

(2) The Company accounts for forfeitures as they occur, rather than estimate expected forfeitures as allowed under GAAP and   therefore do not include a forfeiture rate in our expected to vest calculation unless necessary for a performance condition award.

Summary of Unrecognized Stock-Based Compensation Expense and Weighted Average Period Remaining

A summary of our remaining unrecognized stock-based compensation expense and the weighted average remaining amortization period at June 30, 2017 related to our non-vested stock options and RSU awards is presented below:

	Stock
	Options		RSUs
Unrecognized compensation expense (in millions)	$	59	$	258
Weighted average period remaining (in years)		2.6		3.2