Vessels (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018
Management Agreement
Property Plant And Equipment [Line Items]
Payments for ballast water treatment system and exhaust gas cleaning system installation	$ 16,447	$ 134

The cash outflow for the purchase of a facility and equipment that provides water supply which includes wells, reservoirs, pumping stations, and control facilities; and waste water systems which includes the waste treatment and disposal facility and equipment to households and industry.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 13
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3213-108585

Name:	us-gaap_PaymentsToAcquireWaterAndWasteWaterSystems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration