Operations and summary of significant accounting policies - Disposal Groups, Including Discontinued Operations (Details) - Disposal Group, Held-for-sale, Not Discontinued Operations $ in Thousands	Dec. 31, 2019 USD ($)
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Net Assets Classified as Held for Sale	$ 3,284
AWR Corp.
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Cash	6,015
Accounts receivable, net	9,544
Prepaids and other current assets	291
Property, plant and equipment, net	268
Goodwill	7,593
Intangibles, net	141
Operating lease right-of-use assets	461
Other long-term assets	119
Total Assets	24,432
Accounts payable and accrued liabilities	1,030
Accrued compensation	1,474
Deferred revenue	17,851
Other current liabilities	503
Operating lease liabilities - non-current	290
Total Liabilities	$ 21,148