Allowance For Credit Losses - Activities In Allowance For Credit Losses (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of year	$ 3,469
Additions	7	$ 586
Write-offs	(1,811)
Balance at end of period	$ 1,665	1,371
Cumulative-effect adjustments upon adoption of ASU | Accounting Standards Update 2016-13
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Balance at beginning of year		$ 785