Commitments and Contingencies - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	1 Months Ended	3 Months Ended		6 Months Ended
	May 31, 2013 Employee	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013 M Y	Jun. 30, 2012	Jan. 23, 2012 sqft
Commitments and Contingencies Disclosure [Line Items]
Reduction in workforce	27
Percentage of reduction in workforce	21.00%
Severance charge		$ 0.8	$ 0.6	$ 0.8	$ 0.6
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	0.9	1.2	1.6
Additional charges
Commitments and Contingencies Disclosure [Line Items]
Severance charge		$ 2.1		$ 2.1