Real Estate - Additional Information (Detail) ft² in Thousands, $ in Millions	1 Months Ended	3 Months Ended				9 Months Ended
	Dec. 31, 2007 USD ($) Building	Sep. 30, 2017 USD ($) RenewalOptions	Jun. 30, 2017 USD ($)	Sep. 30, 2016 USD ($)	Mar. 31, 2016 USD ($)	Sep. 30, 2017 USD ($) ft² RenewalOptions Lease_Agreements	Sep. 30, 2016 USD ($)	Dec. 31, 2008 USD ($)
Real Estate Properties [Line Items]
Sale of facility and associated real property	$ 109.0
Mortgage debt retired	47.7
Cash received net of transaction costs and debt retirement	$ 61.0
Leaseback transaction lease period	12 years
Number of building leased | Building	2
Net deferred gain on real estate sale		$ 9.0				$ 9.0		$ 39.1
Deferred gain recognized on real estate sale		0.2		$ 0.9		$ 2.0	$ 2.6
Lease expiration year						2029
Lease security deposit		4.7				$ 4.7
Letter of credit		$ 3.0				$ 3.0
Percentage of management fee included in the base annual rent						3.50%
Lease extension period						10 years
Number of times to renew the lease contract | RenewalOptions		2				2
Subleased area | ft²						16
Rental income from sublease agreement						$ 0.6
Amended Lease Term [Member]
Real Estate Properties [Line Items]
Lease expiration date						Dec. 31, 2029
Percentage reduction in base rental						8.00%
Tenant improvement allowances		$ 13.1				$ 13.1
Lease security deposit		$ 3.0				$ 3.0
Sublease
Real Estate Properties [Line Items]
Number of sublease agreements | Lease_Agreements						1
Reversal of cease use expense			$ 0.5		$ 0.8
Second Sublease
Real Estate Properties [Line Items]
Lease expiration date						2018-03