Significant Accounting Policies - Doubtful Accounts (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Prior to Adoption of ASC 326 [Roll Forward]
Allowance for credit losses, beginning of period		$ 29,387		$ 28,457
Additions charged to expense		11,462		23,782
Adjustment to value of acquired receivables		2,207		2,207
Write-offs, net of recoveries		(12,323)		(23,713)
Allowance for credit losses, end of period		$ 30,733		$ 30,733
After Adoption of ASC 326 [Roll Forward]
Allowance for credit losses, beginning of period	$ 38,094		$ 30,931
Additions charged to expense	11,976		23,147
Adjustment to value of acquired receivables	0		0
Write-offs, net of recoveries	(7,114)		(15,693)
Allowance for credit losses, end of period	42,956		42,956
Cumulative Effect Period of Adoption Adjustment
After Adoption of ASC 326 [Roll Forward]
Allowance for credit losses, beginning of period	$ 0		$ 4,571