Income Taxes - Additional Information (Detail) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Net deferred tax assets	$ 112.1	$ 104.9
Valuation allowance	$ 113.6	$ 106.4

Amount, after allocation of valuation allowances and deferred tax liability, of deferred tax asset attributable to deductible differences and carryforwards, without jurisdictional netting.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32537-109319

Name:	us-gaap_DeferredTaxAssetsLiabilitiesNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant