Significant Accounting Policies - Doubtful Accounts (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses, beginning of period	$ 30,931	$ 28,457
Additions charged to expense	11,171	12,320
Write-offs, net of recoveries	(8,579)	(11,390)
Allowance for credit losses, end of period	38,094	$ 29,387
Cumulative Effect Period of Adoption Adjustment
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for credit losses, beginning of period	$ 4,571