Income Taxes - Schedule of Pre-Tax Income (Loss) and Effective Income Tax Rates (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Income Tax Examination [Line Items]
Pre-Tax Income (Loss)	$ 5.3	$ (46.4)	$ 0.0
Effective Tax Rate	(26.40%)	(16.60%)	0.00%
Bermuda
Income Tax Examination [Line Items]
Pre-Tax Income (Loss)	$ (18.0)	$ (56.2)	$ (34.7)
Effective Tax Rate	0.00%	0.00%	0.00%
United States (Federal)
Income Tax Examination [Line Items]
Pre-Tax Income (Loss)	$ 65.6	$ 103.3	$ 84.7
Effective Tax Rate	18.10%	22.70%	24.60%
United Kingdom
Income Tax Examination [Line Items]
Pre-Tax Income (Loss)	$ (61.1)	$ (100.6)	$ (45.9)
Effective Tax Rate	24.40%	15.70%	14.90%
Barbados
Income Tax Examination [Line Items]
Pre-Tax Income (Loss)	$ 0.0	$ 0.0	$ 0.0
Effective Tax Rate	0.00%	0.00%	0.00%
Belgium
Income Tax Examination [Line Items]
Pre-Tax Income (Loss)	$ 0.0	$ 0.2	$ 0.0
Effective Tax Rate	0.00%	30.70%	15.80%
Brazil
Income Tax Examination [Line Items]
Pre-Tax Income (Loss)	$ 15.3	$ 3.9	$ 5.2
Effective Tax Rate	10.40%	0.00%	0.00%
United Arab Emirates
Income Tax Examination [Line Items]
Pre-Tax Income (Loss)	$ 1.4	$ 2.1	$ 0.4
Effective Tax Rate	0.00%	0.00%	0.00%
Ireland
Income Tax Examination [Line Items]
Pre-Tax Income (Loss)	$ (0.2)	$ 1.8	$ (0.1)
Effective Tax Rate	0.00%	0.00%	0.00%
Italy
Income Tax Examination [Line Items]
Pre-Tax Income (Loss)	$ 1.4	$ 0.6	$ (7.4)
Effective Tax Rate	0.00%	0.00%	0.00%
Malta
Income Tax Examination [Line Items]
Pre-Tax Income (Loss)	$ 0.9	$ (1.4)	$ (2.0)
Effective Tax Rate	0.00%	0.00%	0.00%
Switzerland
Income Tax Examination [Line Items]
Pre-Tax Income (Loss)	$ 0.0	$ (0.1)	$ (0.2)
Effective Tax Rate	0.00%	0.00%	(0.20%)