Credit Losses - Accounts Receivable (Narrative) (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2020	Dec. 31, 2019
Accounts Receivable, Noncurrent, Past Due [Line Items]
Percentage of receivables, current	64.00%
Accounts receivable, net	$ 211,000
Allowance for doubtful accounts	$ 9,383	$ 7,056	$ 3,410	$ 41
Past due less than 60 days
Accounts Receivable, Noncurrent, Past Due [Line Items]
Percentage of receivables, past due	24.00%
Past due less than 120 days
Accounts Receivable, Noncurrent, Past Due [Line Items]
Percentage of receivables, past due	32.00%