Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2023	Sep. 30, 2023	Sep. 30, 2023	Dec. 31, 2022
Components of deferred tax assets and liabilities. [Line Items]
Deferred tax assets, net of valuation allowance	$ 166.2	$ 166.2	$ 166.2
Deferred tax liabilities	9.2	9.2	9.2
Valuation allowance	19.2	19.2	19.2
Reserves for uncertain tax positions	192.2	192.2	192.2	$ 175.9
Unrecognized tax benefits	0.1	0.1	0.1	$ 0.3
Deferred tax expenses related to contract fair value amortization	7.4	16.3
Additional compensation from tax adjustments			$ 20.0
Interest Income And Other, Net
Components of deferred tax assets and liabilities. [Line Items]
Additional compensation from tax adjustments		18.0
Income Tax Benefit (Provision)
Components of deferred tax assets and liabilities. [Line Items]
Additional compensation from tax adjustments		2.0
Foreign Tax Authority
Components of deferred tax assets and liabilities. [Line Items]
Tax benefit related to tax credit refund	2.0	2.0
Foreign Tax Authority | Guyana, Norway, Switzerland And Luxembourg
Components of deferred tax assets and liabilities. [Line Items]
Deferred foreign tax benefits	17.2
Deferred tax benefits related to release of valuation allowance		113.5
Foreign Tax Authority | GUYANA
Components of deferred tax assets and liabilities. [Line Items]
Deferred foreign tax benefits		80.8
Foreign Tax Authority | LUXEMBOURG
Components of deferred tax assets and liabilities. [Line Items]
Deferred foreign tax benefits		18.1
Foreign Tax Authority | SWITZERLAND
Components of deferred tax assets and liabilities. [Line Items]
Deferred foreign tax benefits		10.5
Foreign Tax Authority | NORWAY
Components of deferred tax assets and liabilities. [Line Items]
Deferred foreign tax benefits		4.1
Foreign Tax Authority | Guyana, Australia, Denmark And Luxembourg
Components of deferred tax assets and liabilities. [Line Items]
Tax expenses (benefits) related to various recurring items	$ 63.5
Foreign Tax Authority | GHANA
Components of deferred tax assets and liabilities. [Line Items]
Tax expense (benefit) related to uncertain tax position		(6.8)
Foreign Tax Authority | Mexico
Components of deferred tax assets and liabilities. [Line Items]
Tax expense (benefit) related to uncertain tax position		9.8
Foreign Tax Authority | Guyana, Australia And Luxembourg
Components of deferred tax assets and liabilities. [Line Items]
Tax expenses (benefits) related to various recurring items		$ 131.3