Commitments and Contingencies - Additional Information (Detail) ft² in Thousands, $ in Millions	12 Months Ended
	Dec. 31, 2015 USD ($) CreditFacility ft²	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($) ft²
Commitments and Contingencies Disclosure [Line Items]
Rent expense	$ 16.0	$ 14.6	$ 14.0
Size of office space leased (sqft) | ft²	7		15
Rent reimbursements related to sublease			$ 1.1
Letter of Credit
Commitments and Contingencies Disclosure [Line Items]
Number of letters of credit issued to secure office space leases (credit facility) | CreditFacility	5
Amount outstanding on letters of credit	$ 4.6	$ 5.7