Summary of Significant Accounting Policies - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Cash, cash equivalents and marketable securities	$ 189,400,000
Number of reporting units	1
Unrecognized tax benefits	0
Unrecognized tax benefits, accrued amounts for interest and penalties	0
Amount reclassified out of accumulated other comprehensive (loss) income	0
Number of Operating Segment	1
United States
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Percentage of revenue earned	89.00%	88.00%	94.00%
Percentage of long lived assets	9.00%	10.00%
Maximum
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Cash equivalents original maturity period	3 months
Rhein
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Currency translation adjustments	500,000	400,000	(300,000)
Currency transaction gain (loss)	$ (200,000)	$ (200,000)	$ 200,000