Vessels - Vessel costs, depreciation, impairment and amortization, and carrying amount (Details) $ in Thousands	9 Months Ended
Sep. 30, 2018 USD ($)
Property, Plant and Equipment
As of beginning of period	$ 1,444,146
As of end of period	1,619,630
Total Cost [Member]
Property, Plant and Equipment
As of January 1	1,810,158
Additions	1,714
Transferred from vessels under construction	252,323
Retirement	(1,244)
As of September 30	2,062,951
Total Accumulated Depreciation and Impairment [Member]
Property, Plant and Equipment
As of beginning of period	366,012
Depreciation and amortization	75,053
Impairment charges	3,500
Retirement	(1,244)
As of end of period	$ 443,321

The amount recognised as a reduction of the carrying amount of an asset or cash-generating unit to its recoverable amount. [Refer: Carrying amount [member]]

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 36
-IssueDate 2017-01-01
-Paragraph 130
-Subparagraph b
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=36&date=2017-03-01&anchor=para_130_b&doctype=Standard
-URIDate 2017-03-09

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Name IAS
-Number 36
-IssueDate 2017-01-01
-Paragraph 130
-Subparagraph d
-Clause ii
-URI http://eifrs.ifrs.org/eifrs/XBRL?type=IAS&num=36&date=2017-03-01&anchor=para_130_d_ii&doctype=Standard
-URIDate 2017-03-09

Name:	ifrs-full_ImpairmentLoss
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration