Nature of Business and Accounting Policies - Schedule of Cash, Cash Equivalents, and Restricted Cash (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Accounting Policies [Abstract]
Cash and cash equivalents	$ 3,109,322	$ 2,650,134	$ 1,665,412	$ 1,183,945
Prepaid expenses and other current assets	8,004	4,910	2,114	47,762
Other assets	3,355	3,209	0	0
Cash, cash equivalents and restricted cash per statement of cash flows	$ 3,120,681	$ 2,658,253	$ 1,667,526	$ 1,231,707