Significant Accounting Policies - Doubtful Accounts (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Prior to Adoption of ASC 326 [Roll Forward]
Allowance for credit losses, beginning of period		$ 30,733		$ 28,457	$ 28,457
Additions charged to expense		12,111		35,893
Adjustment to value of acquired receivables		0		2,207
Write-offs, net of recoveries		(11,314)		(35,027)
Allowance for credit losses, end of period		$ 31,530		$ 31,530
After Adoption of ASC 326 [Roll Forward]
Allowance for credit losses, beginning of period	$ 42,956		$ 30,931
Additions charged to expense	11,169		34,316
Adjustment to value of acquired receivables	0		0
Write-offs, net of recoveries	(9,268)		(24,961)
Allowance for credit losses, end of period	44,857		44,857		$ 30,931
Accounting standards update					us-gaap:AccountingStandardsUpdate201613Member
Cumulative Effect Period of Adoption Adjustment
After Adoption of ASC 326 [Roll Forward]
Allowance for credit losses, beginning of period	$ 0		$ 4,571
Allowance for credit losses, end of period					$ 4,571