Accounts Receivable - Allowance for Doubtful Accounts Related to Accounts Receivable (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
Allowance for Doubtful Accounts Receivable [Roll Forward]
Allowance for doubtful accounts beginning of period	$ 21,903	$ 23,842
Provision for bad debts	24,512	18,287
Write-offs	(16,343)	(19,586)
Allowance for doubtful accounts end of period	$ 30,072	$ 22,543