Short-term borrowings (Details) (USD $)			12 Months Ended		12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2011 Hawaiian Electric Company, Inc. and Subsidiaries Institution	Dec. 31, 2011 Parent	Dec. 31, 2011 Interest rate on draws, alternative one Hawaiian Electric Company, Inc. and Subsidiaries	Dec. 31, 2011 Interest rate on draws, alternative two	Dec. 31, 2011 Interest rate on draws, alternative two Hawaiian Electric Company, Inc. and Subsidiaries	Dec. 31, 2011 Interest rate on draws, alternative three	Dec. 31, 2011 Interest rate on draws, alternative three Hawaiian Electric Company, Inc. and Subsidiaries	Dec. 31, 2011 Interest rate on draws, alternative four	Dec. 31, 2011 Interest rate on draws, alternative four Hawaiian Electric Company, Inc. and Subsidiaries	Dec. 31, 2011 Commercial paper Hawaiian Electric Company, Inc. and Subsidiaries	Dec. 31, 2010 Commercial paper Hawaiian Electric Company, Inc. and Subsidiaries
Short-term borrowings
Outstanding amount	$ 68,821,000	$ 24,923,000										$ 69,000,000	$ 25,000,000
Weighted-average interest rate (as a percent)												0.80%	0.90%
Maximum capacity under syndicated credit facilities			175,000,000	125,000,000
Credit agreements
Maximum capacity under syndicated credit facilities			$ 175,000,000	$ 125,000,000
Number of financial institutions			8
Line of credit facility, reference rate			Adjusted LIBO Rate		Adjusted LIBO Rate	Prime Rate	Prime Rate	Federal Funds Rate	Federal Funds Rate	Adjusted LIBO Rate for a one month interest period	Adjusted LIBO Rate for a one month interest period
Line of credit facility basis points (as a percent)			2.25%		1.50%			0.50%	0.50%	0.50%	0.50%
Annual fees on undrawn commitments, basis points (as a percent)			0.25%