Income Taxes - Loss Before Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Income attributable to common stockholders	$ (35,979)	$ (137,842)	$ (131,392)
Loss attributable to noncontrolling interest and redeemable noncontrolling interests	286,843	413,104	395,968
Loss before income taxes	$ 250,864	$ 275,262	$ 264,576