Summary of Significant Accounting Policies - Allowance for Doubtful Accounts Related to Accounts Receivable (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Accounting Policies [Abstract]
Allowance for doubtful accounts beginning of year	$ 19,463	$ 15,315	$ 14,256
Provision for bad debts	18,867	21,896	19,226
Write-offs	(15,913)	(17,748)	(18,167)
Allowance for doubtful accounts end of year	$ 22,416	$ 19,463	$ 15,315