Business and Significant Accounting Policies - Schedule of Cash and Cash Equivalents and Restricted Cash (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents [Abstract]
Cash and cash equivalents	$ 712,583	$ 280,836	$ 156,368	$ 538,908
Restricted cash classified in:
Prepaid expenses and other current assets	0	0	2,295	15,148
Other assets	0	0	0	3,002
Cash classified as held-for-sale	0	0	0	10,000
Cash and cash equivalents and restricted cash per the Consolidated Statements of Cash Flows	$ 712,583	$ 280,836	$ 158,663	$ 567,058