Discontinued operations - Mexico project development- Narratives (Details) $ / shares in Units, gal in Millions					1 Months Ended						3 Months Ended	6 Months Ended	12 Months Ended
	Aug. 28, 2020 USD ($)	Aug. 28, 2020 MXN ($)	Jun. 29, 2020	Aug. 22, 2016 gal	Feb. 28, 2018	Nov. 30, 2015 gal	Feb. 28, 2014 USD ($)	May 31, 2013 USD ($) $ / shares	Feb. 29, 2012 USD ($)	May 31, 2010 gal	Jun. 30, 2020 USD ($)	Jun. 30, 2020 USD ($)	Dec. 31, 2015 gal	Dec. 31, 2020 USD ($) ha	Dec. 31, 2018	Jan. 31, 2018
Schedule of Investments [Line Items]
Period Required To Operate And Maintain Plant And Aqueduct				37 years
Subscription Agreement Description					The Agreement calls for NSC to retain a minimum of 25% of the equity in AdR. One or more affiliates of Greenfield SPV VII, S.A.P.I. de C.V. (“Greenfield”), a Mexico company managed by an affiliate of a leading U.S. asset manager, would acquire a minimum of 55% of the equity of AdR. The Agreement also provided Suez MA with the option to purchase 20% of the equity of AdR. If Suez MA did not exercise this option, NSC would retain 35% of the equity of AdR and Greenfield will acquire 65% of the equity of AdR. The Agreement became effective when the certain conditions precedent related to the Project were met. The aggregate investment to be made by the equity partners in the Project, in the form of equity and subordinated shareholder loans, is presently estimated at approximately 20% of the total cost of Phase 1 of the Project.
Number of days to submit list of non-recoverable expenses made			20 days
Impairment loss on long-lived assets											$ (3,000,000.0)
Adjustment to reduce operating lease right of use assets											2,600,000	$ 2,600,000
Adjustment to reduce operating lease liabilities											$ 2,200,000	2,200,000
Payments For Option Exercised							$ 1,000,000.0
Share Price | $ / shares								$ 1
Aguas de Rosarito S.A.P.I. de C.V [Member]
Schedule of Investments [Line Items]
Equity Method Investment, Ownership Percentage														50.00%
Option agreement [Member]
Schedule of Investments [Line Items]
Payments To Enter Option Agreement									$ 300,000
NSC Agua [Member]
Schedule of Investments [Line Items]
Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners										50.00%
Total Percentage Of Ownership Interest In An Acquired Company										99.99%
Seawater Reverse Osmosis Desalination Plant Per Day Processing Capacity | gal				100						100
Area of Land | ha														20.1
Land														$ 21,100,000
Equity Method Investment, Ownership Percentage														50.00%
Period in which construction must be completed				36 months
Payments for land and rights of way held for development												$ 3,000,000.0
Amount of non-recoverable expenses	$ 51,144,525	$ 137,333,114
Payments For Option Exercised							$ 1,000,000.0
Percentage of Voting Interest Acquired through Option Agreement								25.00%	25.00%
NSC Agua [Member] | Aguas de Rosarito S.A.P.I. de C.V [Member]
Schedule of Investments [Line Items]
Equity Method Investment, Ownership Percentage					0.40%										99.60%
NSC Agua [Member] | First Phase [Member]
Schedule of Investments [Line Items]
Seawater Reverse Osmosis Desalination Plant Per Day Processing Capacity | gal				50		50							50
NSC Agua [Member] | Second Phase [Member]
Schedule of Investments [Line Items]
Seawater Reverse Osmosis Desalination Plant Per Day Processing Capacity | gal				50		50							50
NSC Agua [Member] | Option agreement [Member]
Schedule of Investments [Line Items]
Total Voting Interest Percentage After Conversion Of Loan								99.99%								99.99%
Repayment of inter-company loan payable								$ 5,700,000
Option Agreement Expiration Date									Feb. 07, 2014