Income Taxes - Components of Company's Deferred Tax Assets and Liabilities (Footnote) (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2018 USD ($)
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	$ 826.3
SPAIN
Operating Loss Carryforwards [Line Items]
Tax losses and disallowed finance costs	$ 23.6
Carryforward term (in years)	P18Y
Norway
Operating Loss Carryforwards [Line Items]
Tax losses and disallowed finance costs	$ 15.3
Carryforward term (in years)	P10Y
LUXEMBOURG
Operating Loss Carryforwards [Line Items]
Carryforward term (in years)	P17Y