Allowance for Credit Losses - Allowance for Credit Loss Rollforward (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 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	$ (1,700)	$ 11,800	292	22,436
Deductions			(14,787)	(12,635)
Ending balance	21,606	36,629	21,606	36,629
Accounts receivable, allowance for credit loss	21,400	36,200	21,400	36,200
Contract with customer, asset, allowance for credit loss	$ 200	$ 400	$ 200	$ 400