Stock-based Compensation (Tables)

6 Months Ended

Jun. 30, 2018

Stock-based Compensation

Summary of stock option activity

				Remaining	Aggregate
		Exercise		Contractual Term	Intrinsic Value
	Shares	Price		(in years)	(in thousands)(1)
Balance at December 31, 2017	2,858,158	$	20.37	2.49	$	79,230
Granted	—	$	—	—	$	—
Exercised	(206,363)	$	20.00	—	$	4,903
Forfeited/canceled	—	$	—	—	$	—
Balance at June 30, 2018	2,651,795	$	20.40	1.99	$	57,204
Vested and exercisable as of June 30, 2018	2,651,795	$	20.40	1.99	$	57,204

(1) The aggregate intrinsic value is calculated as the difference between the exercise price of the underlying awards and the closing stock price of our Class A common stock as of the respective date.

Summary of additional information regarding exercisable and vested stock options

	Stock Options Exercisable
	and Vested
		Weighted-
		Average
	Number of	Remaining Life
Range of exercise prices	Shares	(in years)
$20.00	2,531,795	1.95
$28.80	120,000	2.82
$20.00 - $28.80	2,651,795	1.99

Summary of activities for unvested RSUs

	UnvestedRestricted Stock Units
		Weighted-Average
		Grant-Date
	Number of Shares	Fair Value
Unvested at December 31, 2017	1,163,700	$	40.24
Granted	379,480	$	47.26
Vested	(401,959)	$	42.48
Forfeited/canceled	(35,089)	$	47.83
Unvested at June 30, 2018	1,106,132	$	41.60
Expected to vest after June 30, 2018	1,142,464	$	41.64