Lease Obligations - Additional Information (Detail) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020 USD ($) ft²	Jun. 30, 2019 USD ($)	Jun. 30, 2020 USD ($) ft²	Jun. 30, 2019 USD ($)	Feb. 26, 2020 Building	Dec. 31, 2019 USD ($)	Oct. 14, 2019 ft²
Lessee Lease Description [Line Items]
Right-of-use assets	$ 37.1		$ 37.1			$ 39.8
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	us-gaap:OtherAssetsNoncurrent		us-gaap:OtherAssetsNoncurrent			us-gaap:OtherAssetsNoncurrent
Lease liability, current	$ 4.7		$ 4.7			$ 4.4
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List]	us-gaap:AccruedLiabilitiesCurrent		us-gaap:AccruedLiabilitiesCurrent			us-gaap:AccruedLiabilitiesCurrent
Lease liability, noncurrent	$ 44.2		$ 44.2			$ 46.5
Operating Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	us-gaap:OtherLiabilitiesNoncurrent		us-gaap:OtherLiabilitiesNoncurrent			us-gaap:OtherLiabilitiesNoncurrent
Rent expense	$ 1.8	$ 1.4	$ 3.4	$ 3.0
Weighted-average discount rate	7.10%		7.10%
Weighted-average remaining lease term	10 years 1 month 17 days		10 years 1 month 17 days
Dublin Office [Member]
Lessee Lease Description [Line Items]
Approximate square feet of office space | ft²	18,900		18,900				63,000
Deerfield Office [Member]
Lessee Lease Description [Line Items]
Number Of Properties Purchased | Building					3
Lake Forest Office [Member]
Lessee Lease Description [Line Items]
Approximate square feet of office space | ft²	160,000		160,000
Right-of-use assets	$ 17.4		$ 17.4
Novato Office [Member]
Lessee Lease Description [Line Items]
Approximate square feet of office space | ft²	61,000		61,000
Novato Office [Member] | Selling, General and Administrative Expenses [Member]
Lessee Lease Description [Line Items]
Impairment charges	$ 1.1