Summary of Significant Accounting Policies - Allowance for Doubtful Accounts and Other Accounts Receivable Allowances (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Allowance For Doubtful Accounts Receivable Rollforward
Allowance, balance at the beginning	$ 5,945	$ 5,533	$ 5,214
Provision charged to income	4,625	719	314
Accounts written off, net of recoveries	(559)	(307)	5
Allowance, balance at ending	$ 10,011	$ 5,945	$ 5,533