Contract Balances (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2019 USD ($)
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance at Beginning of Period	$ 16,956
Charged to Cost and Expenses	35,359
Deductions	(34,240)
Balance at End of Period	18,075
Balance at Beginning of Period	624,626
Recognition of unearned revenue	(4,128,842)
Deferral of revenue	4,137,995
Balance at End of Period	$ 633,779
Remaining performance obligations	true