Allowance for Credit Losses - Allowance for Credit Loss Rollforward (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	$ 33,368	$ 26,828
Sensis acquisition, balance as of March 1, 2021	2,733
Additions	2,018	10,588
Deductions	(3,318)	(3,630)
Ending balance	34,801	33,786
Accounts receivable, allowance for credit loss	34,600	33,500
Contract with customer, asset, allowance for credit loss	$ 200	$ 300