Commitments and Contingencies - Additional Information (Detail) (USD $)	9 Months Ended		12 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2012	Dec. 31, 2010	Dec. 31, 2013
Loss Contingencies [Line Items]
Operating lease expiration year	2019
Rent expense	$ 2,900,000	$ 2,500,000
Tenant improvement allowances			336,000	639,000
Restricted cash	1,575,000				1,252,000	[1]
Commitments purchased	6,300,000				3,200,000
Period of purchase commitment of inventory from specified date	9 months
Cancelable Lease Agreement [Member]
Loss Contingencies [Line Items]
Penalties	83,000
Motor vehicle lease expenses	$ 2,000,000	$ 1,800,000

[1] The Condensed Consolidated Balance Sheet as of December 31, 2013 has been derived from the audited consolidated financial statements at that date but does not include all of the information and footnotes required by generally accepted accounting principles for complete financial statements.