Cash, Cash Equivalents, and Restricted Cash (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Jun. 30, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Dec. 31, 2017
Cash and Cash Equivalents [Line Items]
Cash and Restricted Cash	$ 4,459,721	$ 5,028,205	$ 3,812,041	$ 3,078,564	$ 3,913,994	$ 2,822,795
Cash and cash equivalents
Cash and Cash Equivalents [Line Items]
Cash and Restricted Cash	4,435,018		3,794,483
Non-current Assets
Cash and Cash Equivalents [Line Items]
Cash and Restricted Cash	24,703		17,558
Cash
Cash and Cash Equivalents [Line Items]
Cash and Restricted Cash	3,037,290		2,588,945
Cash | Cash and cash equivalents
Cash and Cash Equivalents [Line Items]
Cash and Restricted Cash	3,013,907		2,572,685
Cash | Non-current Assets
Cash and Cash Equivalents [Line Items]
Cash and Restricted Cash	23,383		16,260
Level 1 Securities | Money market funds
Cash and Cash Equivalents [Line Items]
Cash and Restricted Cash	1,422,431		1,223,096
Level 1 Securities | Money market funds | Cash and cash equivalents
Cash and Cash Equivalents [Line Items]
Cash and Restricted Cash	1,421,111		1,221,798
Level 1 Securities | Money market funds | Non-current Assets
Cash and Cash Equivalents [Line Items]
Cash and Restricted Cash	$ 1,320		$ 1,298