Revenue Recognition - Accounts Receivable and Deferred Revenue (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Assets
Accounts receivable	$ 78,565	$ 53,351
Liabilities:
Deferred revenue, current portion	50,125	56,016
Deferred revenue, long-term portion	22,805	23,808
Total deferred revenues	72,930	79,824
Current accounts receivable	78,565	53,351
Other noncurrent assets	$ 14,743	$ 12,476