Accounting Policies - Taxation (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Accounting Policies [Abstract]
Income tax expense		$ 5.1
Valuation allowance		5.1
Provisional income tax expense (benefit)	$ (1.9)	$ 2.4
Provisional income tax benefit, adjustment	$ 1.9