Commitments and Contingencies - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	1 Months Ended	3 Months Ended		9 Months Ended			1 Months Ended	3 Months Ended	9 Months Ended
	May 31, 2013 Employee	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013 Y M	Sep. 30, 2012	Jan. 23, 2012 sqft	Sep. 15, 2013 Additional charges Employee	Sep. 30, 2013 Additional charges	Sep. 30, 2013 Additional charges
Commitments and Contingencies Disclosure [Line Items]
Reduction in workforce	27						6
Percentage of reduction in workforce	21.00%
Severance charge		$ 0.8	$ 1.2	$ 0.8	$ 1.8		$ 0.2	$ 2.1	$ 2.1
Office space under lease, square feet						48,000
New lease term, months				123
Number of lease renewal options				2
Number of years lease agreement, renewal option				5
Aggregate minimum lease commitment		15.2		15.2
Letter of credit to secure obligations under lease				1.6
Rent expense charged to operations		$ 0.4	$ 0.4	$ 1.6	$ 1.7