Accounts Receivable - Allowance for Doubtful Accounts Related to Accounts Receivable (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Receivables [Abstract]
Allowance for doubtful accounts beginning of period	$ 22,416	$ 19,463
Provision for bad debts	5,554	4,460
Write-offs	(6,207)	(4,347)
Allowance for doubtful accounts end of period	$ 21,763	$ 19,576