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Retirement benefits Additional Information (Details) - USD ($) | 12 Months Ended |
--- | --- | ---
Dec. 31, 2014 | Dec. 31, 2013 | Dec. 31, 2012 | Dec. 31, 2007
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Vested percentage of interest of each affected participant after participating employer terminates participation | 100.00% |  |  |
Number of years for which regulatory asset/liability for each utility will be amortized, beginning with respective utility's next rate case | 5 years |  |  |
Executive life and nonqualified pension plan expenses | $ 1,200,000 | $ 1,200,000 |  |
Regulatory asset charges pretax | $ 340,000,000 | (364,000,000) |  |
Fair value of plan assets, valuation difference amortized in first year (as a percent) | 0.00% |  |  |
Fair value of plan assets, valuation difference amortized in two to five years (as a percent) | 25.00% |  |  |
Number of past years for adding or subtracting the unamortized differences from fair value | 4 years |  |  |
Percentage of range around fair value | 15.00% |  |  |
Expected cash funding for qualified defined benefit plans |  |  |  |
Defined contribution plan, expenses recognized | $ 5,000,000 | 5,000,000 | $ 4,000,000 |
Cash contributions by the employer to defined contribution plan | $ 5,000,000 | 4,000,000 | 4,000,000 |
Minimum |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Threshold percentage around fair value | 85.00% |  |  |
Maximum |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Threshold percentage around fair value | 115.00% |  |  |
Hawaiian Electric Company, Inc. and Subsidiaries |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Regulatory assets | $ 833,843,000 | 506,186,000 |  |
Retirement benefits expense | $ 32,000,000 | 30,000,000 | $ 32,000,000 |
Expected cash funding for qualified defined benefit plans |  |  |  |
Maximum percentage of participant deferrals eligible for Employer contribution match, towards defined contribution plan | 6.00% |  |  |
Employer's additional matching contribution on employee deferrals (as a percent) | 50.00% |  |  |
Defined contribution plan, expenses recognized | $ 900,000 | 600,000 |  |
American Savings Bank (ASB) |  |  |  |
Expected cash funding for qualified defined benefit plans |  |  |  |
Maximum percentage of participant deferrals eligible for Employer contribution match, towards defined contribution plan | 4.00% |  |  |
Hawaii Electric Light Company, Inc. (HELCO) |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Regulatory assets | $ 107,454,000 | 64,552,000 |  | $ 12,800,000
Regulatory assets recovery period | 5 years |  |  |
Hawaiian Electric Company, Inc (HECO) |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Regulatory assets | $ 623,784,000 | $ 381,346,000 |  |
Pension benefits |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Expected rate of return on plan assets (as a percent) | 7.75% |  |  |
Discount rate (as a percent) | 4.22% | 5.09% | 4.13% |
Pension expense | $ 32,000,000 | $ 34,000,000 | $ 35,000,000 |
Defined benefit pension plans with accumulated benefit obligations in excess of plan assets |  |  |  |
Aggregate accumulated benefit obligations | 1,500,000,000 | 1,200,000,000 |  |
Plan assets | 1,200,000,000 | 1,100,000,000 |  |
Defined benefit plans with benefit obligations in excess of plan assets |  |  |  |
Aggregate projected benefit obligations | 1,700,000,000 | 1,400,000,000 |  |
Plan assets | 1,200,000,000 | 1,100,000,000 |  |
Expected cash funding for qualified defined benefit plans |  |  |  |
Estimate of contributions to postretirement benefit plans in 2015 | 85,000,000 | 0 |  |
Pension benefits | Hawaiian Electric Company, Inc. and Subsidiaries |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Pension expense | 31,000,000 | 30,000,000 | $ 32,000,000 |
Defined benefit pension plans with accumulated benefit obligations in excess of plan assets |  |  |  |
Aggregate accumulated benefit obligations | 1,500,000,000 | 1,200,000,000 |  |
Plan assets | 1,100,000,000 | $ 1,058,260,000 |  |
Expected cash funding for qualified defined benefit plans |  |  |  |
Estimate of contributions to postretirement benefit plans in 2015 | $ 83,000,000 |  |  |
Other benefits |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Discount rate (as a percent) | 4.17% | 5.03% | 4.07% |
Assumed health care trend rate for medical in next fiscal year (as a percent) | 7.25% | 7.50% |  |
Assumed health care trend rate for grading down in 2024 and thereafter (as a percent) | 5.00% | 5.00% |  |
Assumed health care trend rate for dental in next fiscal year (as a percent) | 5.00% | 5.00% |  |
Assumed health care trend rate for vision in next fiscal year (as a percent) | 4.00% | 4.00% |  |
Age threshold health care trend rates are adjusted | 65 years |  |  |
Percentage by which medical trend for post-65 is higher than pre-65, 2014 | 4.00% |  |  |
Percentage by which medical trend for post-65 is higher than pre-65, 2015 | 3.00% |  |  |
Postretirement benefits other than pension expense | $ 1,200,000 | $ 400,000 | $ 1,000,000 |
Effect of one-percentage-point increase in assumed health care cost trend rates that would have increased total service and interest cost | 200,000 |  |  |
Effect of one-percentage-point increase in assumed health care cost trend rates that would have increased the accumulated postretirement benefit obligation (APBO) | 3,800,000 |  |  |
Effect of one-percentage-point decrease that would have reduced total service and interest cost | 300,000 |  |  |
Effect of one-percentage-point decrease that would have reduced APBO | 4,600,000 |  |  |
Defined benefit pension plans with accumulated benefit obligations in excess of plan assets |  |  |  |
Aggregate accumulated benefit obligations |  | 400,000 |  |
Expected cash funding for qualified defined benefit plans |  |  |  |
Estimate of contributions to postretirement benefit plans in 2015 | 500,000 |  |  |
2015 | 76,000,000 |  |  |
2016 | 79,000,000 |  |  |
2017 | 83,000,000 |  |  |
2018 | 87,000,000 |  |  |
2019 | 91,000,000 |  |  |
2020 through 2024 | 520,000,000 |  |  |
Other benefits | Hawaiian Electric Company, Inc. and Subsidiaries |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Postretirement benefits other than pension expense | 1,000,000 | $ 0 | $ 400,000 |
Effect of one-percentage-point increase in assumed health care cost trend rates that would have increased total service and interest cost | 200,000 |  |  |
Effect of one-percentage-point increase in assumed health care cost trend rates that would have increased the accumulated postretirement benefit obligation (APBO) | 3,700,000 |  |  |
Effect of one-percentage-point decrease that would have reduced total service and interest cost | 300,000 |  |  |
Effect of one-percentage-point decrease that would have reduced APBO | 4,500,000 |  |  |
Expected cash funding for qualified defined benefit plans |  |  |  |
Estimate of contributions to postretirement benefit plans in 2015 | 500,000 |  |  |
2015 | 70,000,000 |  |  |
2016 | 73,000,000 |  |  |
2017 | 76,000,000 |  |  |
2018 | 79,000,000 |  |  |
2019 | 83,000,000 |  |  |
2020 through 2024 | $ 476,000,000 |  |  |

X
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- Definition An assumption for the next fiscal year as to the rate of return on plan assets reflecting the average rate of earnings expected on the funds invested or to be invested to provide for the benefits included in the benefit obligation. + References No definition available. + Details
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- Definition The assumed health care cost trend rate for the next year used to measure the expected cost of benefits covered by the dental plan under the defined benefit plan (gross eligible charges). This is based upon the annual rate of change in the cost of health care benefits currently provided by the postretirement benefit plan, due to factors other than changes in the composition of the plan population by age and dependency status. + References No definition available. + Details
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- Definition The assumed health care cost trend rate that will be graded down to and used for the 8th fiscal year and thereafter to measure the expected cost of benefits covered by the medical plan under the defined benefit plan (gross eligible charges). This is based upon the annual rate of change in the cost of health care benefits currently provided by the postretirement benefit plan, due to factors other than changes in the composition of the plan population by age and dependency status. + References No definition available. + Details
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- Definition The assumed health care cost trend rate for the next year used to measure the expected cost of benefits covered by the vision plan under the defined benefit plan (gross eligible charges). This is based upon the annual rate of change in the cost of health care benefits currently provided by the postretirement benefit plan, due to factors other than changes in the composition of the plan population by age and dependency status. + References No definition available. + Details
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- Definition Represents the number of past years for adding or subtracting the unamortized differences from the fair value. + References No definition available. + Details
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- Definition Represents the number of years for which regulatory asset/liability for each utilities will be amortized, beginning with the respective utility's next rate case. + References No definition available. + Details
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- Definition Represents the percentage of valuation difference of plan assets amortized in the first year to determine market related value. + References No definition available. + Details
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- Definition Represents the vested percentage of interest of each affected participant if a participating employer terminates its participation in the plans up to the extent funded. + References No definition available. + Details
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- Definition Amount of effect of a one-percentage-point decrease in the assumed health care cost trend rates on the aggregate of the service and interest cost components of net periodic postretirement health care benefit costs. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (m) -URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920 + Details
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- Definition The effect of a one-percentage-point increase in the assumed health care cost trend rates on the accumulated postretirement benefit obligation for health care benefits. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (m) -URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920 + Details
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- Definition Amount of benefits from a defined benefit plan expected to be paid in the five fiscal years after the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (f) -URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920 + Details
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- Definition Amount of benefits from a defined benefit plan expected to be paid in the next fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (f) -URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920 + Details
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- Definition If aggregate disclosures are presented, the aggregate fair value of plan assets for plans with benefit obligations in excess of plan assets as of the measurement date of each statement of financial position presented. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 3 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e2417-114920 + Details
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- Definition Amount of employer's best estimate of contributions expected to be paid to the plan during the next fiscal year beginning after the date of the latest statement of financial position. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (g) -URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920 + Details
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- Definition The amount of the cost recognized during the period for defined contribution plans. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 70 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6414718&loc=d3e28014-114942 + Details
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- Definition The amount of costs recognized during the period for non-pension postretirement benefits, such as medical, dental and life insurance. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (q) -URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=35743120&loc=d3e1928-114920 + Details
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