Income Taxes - Operating and capital loss carryforwards available (Details) - Dec. 31, 2023 £ in Millions, $ in Millions	USD ($)	GBP (£)
U.S. \| Expiring 2024 - 2041
Operating and capital loss carryforwards [Line Items]
Operating loss carryforwards	$ 10
United Kingdom
Operating and capital loss carryforwards [Line Items]
Operating loss carryforwards	$ 38	£ 30

Amount of operating loss carryforward, before tax effects, available to reduce future taxable income under enacted tax laws.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482685/740-10-50-3

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