Supplemental Financial Statement Information - Summary of Rollforward of Insurance Reserve (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Balance Sheet Components Disclosure [Abstract]
Beginning balance	$ 810,273	$ 376,538
Losses paid	(205,629)	(95,881)
Change in estimates for prior periods	137,840	3,392
Reserves for current period	464,896	290,868
Ending balance	$ 1,207,380	$ 574,917