Taxation (Narrative) (Details) - USD ($)		12 Months Ended
	Dec. 22, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Mar. 31, 2015	Dec. 31, 2014
Operating Loss Carryforwards [Line Items]
Tax cuts and jobs act of 2017, incomplete accounting, change in tax rate, deferred tax asset, provisional income tax	$ 36,700,000
Change in valuation allowance		$ 11,200,000	$ 900,000	$ (43,800,000)
Valuation allowance		30,016,000	18,776,000
Income taxes paid (refunded)		343,000	(1,118,000)	$ 10,300,000
Unrecognized tax benefits		0	0
Interest and penalties accrued on unrecognized tax benefits		$ 0	$ 0
Internal Revenue Service (IRS)
Operating Loss Carryforwards [Line Items]
Expected tax rate		5.00%
Foreign statutory income tax rate		35.00%
Valuation allowance					$ 1,000,000	$ 48,500,000
Operating loss carryforwards		$ 162,400,000
Domestic
Operating Loss Carryforwards [Line Items]
Statutory income tax rate		0.00%
U.K.
Operating Loss Carryforwards [Line Items]
Foreign statutory income tax rate		19.30%
Change in valuation allowance		$ 12,100,000
Operating loss carryforwards		$ 124,800,000
Singapore
Operating Loss Carryforwards [Line Items]
Foreign statutory income tax rate		17.00%
Operating loss carryforwards		$ 19,500,000
Ireland
Operating Loss Carryforwards [Line Items]
Foreign statutory income tax rate		12.50%
Operating loss carryforwards		$ 4,700,000