Additional Cash Flow Information - Additional Cash Flow (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Restricted Cash and Cash Equivalents Items [Line Items]
Cash and cash equivalents	$ 5,988,187	$ 3,109,322	$ 2,650,134	$ 1,665,412
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Total	5,988,845	3,120,681	2,658,253	1,667,526
Prepaid expenses and other current assets
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash and cash equivalents	658	8,004	4,910	2,114
Other assets
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash and cash equivalents	$ 0	$ 3,355	$ 3,209	$ 0