Accounts Receivable - Allowance for Doubtful Accounts Related to Accounts Receivable (Detail) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014
Receivables [Abstract]
Allowance for doubtful accounts beginning of period	$ 23,842	$ 22,416
Provision for bad debts	18,287	18,109
Write-offs	(19,586)	(17,234)
Allowance for doubtful accounts end of period	$ 22,543	$ 23,291