Income Taxation - Deferred Tax Ending Balance (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Segment Reporting Information [Line Items]
Net Deferred Tax Asset	$ 154,910
Net Deferred Tax Liability		$ (418)
United States
Segment Reporting Information [Line Items]
Net Deferred Tax Asset	169,891	5,151
United Kingdom
Segment Reporting Information [Line Items]
Net Deferred Tax Liability	(16,074)	(8,377)
Other
Segment Reporting Information [Line Items]
Net Deferred Tax Asset	$ 1,093	$ 2,808