Commitments and Contingencies - Series A Convertible Redeemable Preferred Stock Offering (Details) $ in Thousands			3 Months Ended	12 Months Ended
	Feb. 06, 2017 shares	Dec. 04, 2016 USD ($) shares	Mar. 31, 2017 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Subsidiary, Sale of Stock [Line Items]
Accretion of redeemable noncontrolling interests and equity						$ (263)
Additional paid-in capital
Subsidiary, Sale of Stock [Line Items]
Accretion of redeemable noncontrolling interests and equity						(263)
Series A Convertible Redeemable Preferred Stock
Subsidiary, Sale of Stock [Line Items]
Basis point decrease in dividends accrual rate		0.0075
Accretion of redeemable noncontrolling interests and equity				$ 200,006	$ 292,450	1,719
Total redeemable noncontrolling interests and equity				0	400,276
Series A Convertible Redeemable Preferred Stock | Additional paid-in capital
Subsidiary, Sale of Stock [Line Items]
Accretion to redemption value				61,974	292,450	$ 1,719
Series A Redeemable Convertible Preferred Stock - Beneficial Conversion Feature
Subsidiary, Sale of Stock [Line Items]
Accretion of redeemable noncontrolling interests and equity				$ (13,709)	(265,368)
Series A Redeemable Convertible Preferred Stock - Beneficial Conversion Feature | Additional paid-in capital
Subsidiary, Sale of Stock [Line Items]
Accretion of redeemable noncontrolling interests and equity					$ (265,368)
Accretion period					1 year
Private Placement
Subsidiary, Sale of Stock [Line Items]
Net proceeds from sale of stock		$ 400,000
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) | shares		400,000
IPO | Class A Common Stock
Subsidiary, Sale of Stock [Line Items]
Net proceeds from sale of stock			$ 456,359
Sale of stock, number of shares issued in transaction (in shares) | shares	35,000,000