Accounts Receivable - Allowance for Doubtful Accounts Related to Accounts Receivable (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019		Sep. 30, 2018
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Allowance for doubtful accounts beginning of period	$ 59,963		$ 46,031
Provision for bad debts	54,735	[1]	43,520
Write-offs	(50,035)		(37,529)
Allowance for doubtful accounts end of period	$ 64,663		$ 52,022

[1] Reflects the impact of the Company's adoption of ASU 2016-02 "Leases", on January 1, 2019, using the modified retrospective transition method. Under this method, financial results reported in periods prior to 2019 are unchanged. Refer to footnote 2.