Commitments and Contingencies (Details)		12 Months Ended
	Jul. 31, 2015 USD ($)	Dec. 31, 2015 USD ($) ft²	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
2016		$ 6,124,000
2017		5,851,000
2018		5,435,000
2019		4,961,000
2020		4,602,000
Thereafter		10,632,000
Total		37,605,000
Operating leases, expense		$ 6,300,000	$ 6,600,000	$ 5,500,000
Settlement amount to (against)	$ (14,000,000.0)
Lease with New York Landlord
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
Operating leases, period of free rent		12 months
Allowance from landlord for office improvements and other payments, utilized		$ 1,900,000
Lease with New York Landlord | Office Building
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
Area leased (in sq. ft.) | ft²		43,304
Leases term		10 years
Lease with Massachusetts Landlord
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
Operating leases, period of free rent		3 months
Allowance from landlord for office improvements and other payments, utilized		$ 2,300,000
Lease with Massachusetts Landlord | Office Building
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
Area leased (in sq. ft.) | ft²		51,325
Leases term		10 years 3 months