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Property, plant and equipment - Schedule of Plant, Property and Equipment (Detail) - USD ($) $ in Thousands | Dec. 31, 2018 | Dec. 31, 2017
--- | --- | ---
Property, Plant and Equipment [Line Items] |  |
Cost | $ 7,406,319 | $ 7,125,369
Accumulated depreciation | 1,012,761 | 820,472
Net book value | 6,393,558 | 6,304,897
Land |  |
Property, Plant and Equipment [Line Items] |  |
Cost | 73,773 | 71,689
Accumulated depreciation | 0 | 0
Net book value | 73,773 | 71,689
Equipment and other |  |
Property, Plant and Equipment [Line Items] |  |
Cost | 88,757 | 91,233
Accumulated depreciation | 41,295 | 37,104
Net book value | 47,462 | 54,129
Generation |  |
Property, Plant and Equipment [Line Items] |  |
Cost | 2,470,279 | 2,382,279
Accumulated depreciation | 450,230 | 394,509
Net book value | 2,020,049 | 1,987,770
Generation | Construction in progress |  |
Property, Plant and Equipment [Line Items] |  |
Cost | 104,996 | 209,979
Accumulated depreciation | 0 | 0
Net book value | 104,996 | 209,979
Liberty Utilities Group |  |
Property, Plant and Equipment [Line Items] |  |
Cost | 4,455,935 | 4,205,823
Accumulated depreciation | 521,236 | 388,859
Net book value | 3,934,699 | 3,816,964
Liberty Utilities Group | Construction in progress |  |
Property, Plant and Equipment [Line Items] |  |
Cost | 212,579 | 164,366
Accumulated depreciation | 0 | 0
Net book value | $ 212,579 | $ 164,366

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- Definition Amount before accumulated depreciation, depletion and amortization of physical assets used in the normal conduct of business and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, and furniture and fixtures. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 360 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=6391035&loc=d3e2868-110229 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.13) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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- Definition Amount after accumulated depreciation, depletion and amortization of physical assets used in the normal conduct of business to produce goods and services and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, and furniture and fixtures. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(13)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(14)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03(a)(8)) -URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 360 -SubTopic 10 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6391035&loc=d3e2868-110229 + Details
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