Income Taxes - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2018	Dec. 31, 2017
Income Tax Contingency [Line Items]
Tax cuts and jobs act of 2017, incomplete accounting, provisional income tax expense (benefit)	$ 0.3		$ 7.6
Deferred tax assets, state NOLs	2.5	$ 2.5
Deferred tax assets, federal NOLs	1.5	1.5
Liability for unrecognized tax benefits			5.2
Threshold to favorably impact effective tax rate	5.3	5.3
Unrecognized tax benefits, accrued interest	0.1	0.1	$ 0.1
AUSTRALIA
Income Tax Contingency [Line Items]
Deferred tax assets, foreign NOLs	8.9	8.9
UNITED KINGDOM
Income Tax Contingency [Line Items]
Deferred tax assets, foreign NOLs	1.4	1.4
GERMANY
Income Tax Contingency [Line Items]
Deferred tax assets, foreign NOLs	0.1	0.1
Federal
Income Tax Contingency [Line Items]
Federal research and development credit carry forwards		0.1
State
Income Tax Contingency [Line Items]
Liability for unrecognized tax benefits	$ 0.1	0.1
State | ARIZONA
Income Tax Contingency [Line Items]
State research and development credit carry forwards		$ 9.7