Revenue from Contracts with Customers - Contract Balances (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019	Dec. 31, 2018
Contract Balances
Receivables, which are included in accounts receivable, net	$ 64,658	$ 29,304
Contract assets	0	0
Contract liabilities, which are included in deferred revenue	$ 145,498	$ 97,629	$ 85,736

Amount, after allowance for credit loss, of right to consideration from customer for product sold and service rendered in normal course of business, classified as current.

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