Accounts Receivable - Allowance for Doubtful Accounts Related to Accounts Receivable (Detail) (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013
Receivables [Abstract]
Allowance for doubtful accounts beginning of period	$ 22,416	$ 19,463
Provision for bad debts	12,283	9,199
Write-offs	(11,945)	(8,422)
Allowance for doubtful accounts end of period	$ 22,754	$ 20,240