Accounts Receivable - Allowance for Doubtful Accounts Related to Accounts Receivable (Detail) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014
Receivables [Abstract]
Allowance for doubtful accounts beginning of period	$ 23,842	$ 22,416
Provision for bad debts	13,022	12,283
Write-offs	(14,464)	(11,945)
Allowance for doubtful accounts end of period	$ 22,400	$ 22,754