Income Taxes - Operating and capital loss carryforwards available (Details) - Dec. 31, 2021 £ in Millions, $ in Millions	USD ($)	GBP (£)
U.S. \| Expiring 2022 - 2041
Operating and capital loss carryforwards [Line Items]
Operating loss carryforwards	$ 56
United Kingdom
Operating and capital loss carryforwards [Line Items]
Operating loss carryforwards	$ 37	£ 28

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
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=121826272&loc=d3e32559-109319

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