Supplemental Disclosure to Statements of Cash Flows - Cash (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018	Sep. 30, 2018	Dec. 31, 2017
Cash and Cash Equivalents, at Carrying Value [Abstract]
Cash and cash equivalents	$ 514,882	$ 84,923	$ 17,770	$ 11,882
Restricted cash	14,006	10,899	13,371	13,803
Cash, cash equivalents and restricted cash	$ 528,888	$ 95,822	$ 31,141	$ 25,685