Commitments and Contingencies - Series A Convertible Redeemable Preferred Stock Offering (Details) - USD ($)			2 Months Ended	3 Months Ended
	Apr. 23, 2018	Feb. 06, 2017	Jan. 31, 2017	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Subsidiary, Sale of Stock [Line Items]
Proceeds from issuance of convertible redeemable preferred stock, net of issuance costs				$ 0	$ 55,290,000
Payment of dividends on Series A Preferred Stock				9,719,000	$ 0
Series A Convertible Redeemable Preferred Stock
Subsidiary, Sale of Stock [Line Items]
Accretion of redeemable noncontrolling interests and equity				57,324,000
Total redeemable noncontrolling interests and equity				447,881,000		$ 400,276,000
Series A Convertible Redeemable Preferred Stock | Additional paid-in capital
Subsidiary, Sale of Stock [Line Items]
Accretion of redeemable noncontrolling interests and equity				57,324,000
Series A Redeemable Convertible Preferred Stock - Beneficial Conversion Feature
Subsidiary, Sale of Stock [Line Items]
Accretion of redeemable noncontrolling interests and equity				$ (265,368,000)
Series A Redeemable Convertible Preferred Stock - Beneficial Conversion Feature | Additional paid-in capital
Subsidiary, Sale of Stock [Line Items]
Accretion period				1 year
Series A Preferred Stock
Subsidiary, Sale of Stock [Line Items]
Payment of dividends on Series A Preferred Stock				$ 9,719,000
Class A Common Stock
Subsidiary, Sale of Stock [Line Items]
Common stock, par value (in dollars per share)		$ 0.004		$ 0.004		$ 0.004
Private Placement | Series A Convertible Redeemable Preferred Stock
Subsidiary, Sale of Stock [Line Items]
Sale of stock, number of shares agreed to be issued in transaction (in shares)			400,000
Proceeds from issuance of convertible redeemable preferred stock, net of issuance costs			$ 400,000,000
Period for conversion of stock after first anniversary of initial public offering		1 day
Subsequent Event | Class A Common Stock
Subsidiary, Sale of Stock [Line Items]
Common stock, par value (in dollars per share)	$ 0.004
Subsequent Event | Private Placement | Series A Convertible Redeemable Preferred Stock
Subsidiary, Sale of Stock [Line Items]
Number of shares converted (in shares)	36,143,000