Stock Based Awards and Other Equity Instruments (Tables)

12 Months Ended

Dec. 31, 2016

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Amount of Stock-Based Compensation Expense Related to Stock-Based Awards, Primarily Stock Options and RSUs

The following table presents the amount of stock-based compensation expense related to stock-based awards, primarily stock options and RSUs, on our consolidated statements of operations during the periods presented:

	Year ended December 31,
	2016			2015			2014
	(in millions)
Selling and marketing	$	20		$	16		$	13
Technology and content		40			28			27
General and administrative		25			28			23
Total stock-based compensation expense		85			72			63
Income tax benefit from stock-based compensation    expense		(31	)		(26	)		(24	)
Total stock-based compensation expense, net of    tax effect	$	54		$	46		$	39

Summary of Stock Option

A summary of our stock option activity is presented below:

				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, 2015		5,720		$	53.71
Granted		1,064			63.43
Exercised (1)		(733	)		31.58
Cancelled or expired		(233	)		70.76
Options outstanding as of December 31, 2016		5,818		$	57.60		5.5	$	25
Exercisable as of December 31, 2016		2,796		$	42.95		4.3	$	24

(1) Inclusive of 318,773 options, which were not converted into shares due to net share settlement in order to cover the aggregate exercise price and the minimum amount of required employee withholding taxes. Potential shares which 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 consolidated statements of cash flows.

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:

	December 31,
	2016			2015			2014
Risk free interest rate		1.20	%		1.58	%		1.79	%
Expected term (in years)		4.85			5.42			5.80
Expected volatility		41.81	%		41.79	%		44.04	%
Expected dividend yield	—  %			—  %			—  %

Summary of RSU Activity

The following table presents a summary of our RSU activity:

				Weighted
				Average
				Grant-		Aggregate
	RSUs			Date Fair		Intrinsic
	Outstanding			Value Per Share		Value
	(in thousands)					(in millions)
Unvested RSUs outstanding as of December 31, 2015		1,750		$	79.02
Granted		2,016			63.71
Vested and released (1)		(627	)		76.02
Cancelled		(283	)		73.06
Unvested RSUs outstanding as of December 31, 2016		2,856		$	69.35	$	132

(1) Inclusive of 173,429 RSUs withheld to satisfy employee minimum tax withholding requirements due to net share settlement. 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 consolidated statements of cash flows.

Summary of Unrecognized Compensation Expense and Weighted Average Period Remaining

A summary of our remaining unrecognized compensation expense and the weighted average remaining amortization period at December 31, 2016 related to our non-vested stock options and RSU awards is presented below (in millions, except per year information):

	Stock
	Options		RSUs
Unrecognized compensation expense	$	48	$	149
Weighted average period remaining (in years)		2.3		2.8