Basis of presentation (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Jan. 01, 2019	Dec. 31, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease, liability	$ 241,340		$ 0
Operating lease right-of-use assets	241,486		0
Hawaiian Electric Company, Inc. and Subsidiaries
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease, liability	221,000
Operating lease right-of-use assets	$ 221,261		$ 0
ASU 2016-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease, liability		$ 257,000
Operating lease right-of-use assets		257,000
ASU 2016-02 | Power Purchase Agreement
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease, liability		215,000
Operating lease right-of-use assets		215,000
ASU 2016-02 | Hawaiian Electric Company, Inc. and Subsidiaries
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease, liability		236,000
Operating lease right-of-use assets		$ 236,000