Income Taxes - Summary Of Earliest Tax Years Open To Examination (Details)	12 Months Ended
	Dec. 31, 2016
United States [Member]
Income Tax Examination [Line Items]
Earliest tax years open to examination by tax authorities	2013
United Kingdom [Member]
Income Tax Examination [Line Items]
Earliest tax years open to examination by tax authorities	2012
Norway Member
Income Tax Examination [Line Items]
Earliest tax years open to examination by tax authorities	2006
Angola Member
Income Tax Examination [Line Items]
Earliest tax years open to examination by tax authorities	2013
Brazil [Member]
Income Tax Examination [Line Items]
Earliest tax years open to examination by tax authorities	2010
Australia [Member]
Income Tax Examination [Line Items]
Earliest tax years open to examination by tax authorities	2012