Redeemable Convertible Preferred Stock, Common Stock, and Stockholders' Deficit (Tables)

3 Months Ended

Mar. 31, 2019

Equity [Abstract]

Summary of Activity in Restricted Common Stock

The following table summarizes the activity related to the Company’s restricted common stock for the three months ended March 31, 2019. For purposes of this table, vested restricted common stock represents the shares for which the service condition had been fulfilled as of the three months ended March 31, 2019 (in thousands, except per share amounts):

	Number of Shares		Weighted-average Grant-Date Fair Value per Share
Unvested restricted common stock as of December 31, 2018	898		$	30.33
Granted	—		$	—
Vested	(209	)	$	34.82
Canceled	(32	)	$	34.86
Unvested restricted common stock as of March 31, 2019	657		$	28.68

Summary of Stock Options and SAR Activity

A summary of stock option and SAR activity for the three months ended March 31, 2019 is as follows (in millions, except share amounts which are reflected in thousands, per share amounts, and years):

	SARs Outstanding Number of SARs		Options Outstanding Number of Shares		Weighted-Average Exercise Price Per Share		Weighted-Average Remaining Contractual Life (in years)	Aggregate Intrinsic Value
As of December 31, 2018	758		42,936		$	9.22	5.74	$	1,456
Awards granted	53		250		$	42.52
Awards exercised	—		(677	)	$	3.01
Awards forfeited	(8	)	(43	)	$	32.10
As of March 31, 2019	803		42,466		$	9.51	5.51	$	1,808
Vested and expected to vest as of March 31, 2019	621		35,337		$	4.19	5.14	$	1,694
Exercisable as of March 31, 2019	621		36,245		$	4.95	5.22	$	1,709

Schedule of Restricted Stock Units Activity

The following table summarizes the activity related to the Company’s RSUs for the three months ended March 31, 2019. For purposes of this table, vested RSUs represent the shares for which the service condition had been fulfilled as of March 31, 2019 (in thousands, except per share amounts):

	Number of Shares		Weighted-Average Grant-Date Fair Value per Share
Unvested and outstanding as of December 31, 2018	75,835		$	37.20
Granted	31,476		$	42.52
Vested	(8,694	)	$	34.35
Canceled	(1,713	)	$	23.84
Unvested and outstanding as of March 31, 2019	96,904		$	39.42
Vested and outstanding as of March 31, 2019	71,307		$	28.93

Schedule of Stock-Based Compensation Expense by Function

The following table summarizes total stock-based compensation expense by function for the three months ended March 31, 2018 and 2019 (in millions):

	Three Months Ended March 31,
	2018		2019
Operations and support	$	5	$	1
Sales and marketing	4		1
Research and development	6		3
General and administrative	48		6
Total	$	63	$	11

Schedule of Fair Value Assumptions, SARs and Performance Awards

Awards with market-based targets granted was determined using a Monte Carlo model with the following weighted-average assumptions:

	Three Months Ended March 31,
	2018		2019
Risk-free interest rate	2.8	%	2.7	%
Expected volatility	39.0	%	39.0	%
Expected dividend yield	—	%	—	%

The fair value of stock options and SARs granted was determined using the Black-Scholes option pricing model with the following weighted-average assumptions:

	Three Months Ended March 31,
	2018		2019
Expected term (in years)	5.7		5.9
Risk-free interest rate	2.7	%	2.3	%
Expected volatility	32.6	%	34.9	%
Expected dividend yield	—	%	—	%