XML 24 R24.htm IDEA: XBRL DOCUMENT
v2.4.0.8

Employee benefit plans | 6 Months Ended
--- | ---
Jun. 30, 2013
Employee Benefit Plans [Abstract] |
Pension and Other Postretirement Benefits Disclosure | Employee benefit plans The Company has noncontributory defined benefit pension plans and other postretirement benefit plans for certain eligible employees. Components of net periodic benefit cost for the Company's pension and other postretirement benefit plans were as follows:
|  |  | Other
|  |  | Postretirement
| Pension Benefits | Benefits
Three Months Ended June 30, | 2013 |  | 2012 |  | 2013 |  | 2012 |
| (In thousands)
Components of net periodic benefit cost: |  |  |  |
Service cost | $ | 37 |  | $ | 350 |  | $ | 334 |  | $ | 461 |
Interest cost | 4,106 |  | 4,262 |  | 667 |  | 1,038 |
Expected return on assets | (4,875 | ) | (5,845 | ) | (1,065 | ) | (1,201 | )
Amortization of prior service cost (credit) | 18 |  | (21 | ) | (364 | ) | (272 | )
Amortization of net actuarial loss | 1,716 |  | 2,102 |  | 407 |  | 887 |
Amortization of net transition obligation | — |  | — |  | — |  | 531 |
Net periodic benefit cost, including amount capitalized | 1,002 |  | 848 |  | (21 | ) | 1,444 |
Less amount capitalized | 158 |  | 196 |  | 61 |  | 183 |
Net periodic benefit cost (credit) | $ | 844 |  | $ | 652 |  | $ | (82 | ) | $ | 1,261 |
|  |  | Other
|  |  | Postretirement
| Pension Benefits | Benefits
Six Months Ended June 30, | 2013 |  | 2012 |  | 2013 |  | 2012 |
| (In thousands)
Components of net periodic benefit cost: |  |  |  |
Service cost | $ | 77 |  | $ | 695 |  | $ | 838 |  | $ | 873 |
Interest cost | 8,124 |  | 8,816 |  | 1,607 |  | 2,181 |
Expected return on assets | (9,958 | ) | (11,731 | ) | (2,172 | ) | (2,445 | )
Amortization of prior service cost (credit) | 36 |  | (42 | ) | (728 | ) | (544 | )
Amortization of net actuarial loss | 3,580 |  | 3,783 |  | 1,078 |  | 1,413 |
Amortization of net transition obligation | — |  | — |  | — |  | 1,063 |
Net periodic benefit cost, including amount capitalized | 1,859 |  | 1,521 |  | 623 |  | 2,541 |
Less amount capitalized | 268 |  | 430 |  | 90 |  | 321 |
Net periodic benefit cost | $ | 1,591 |  | $ | 1,091 |  | $ | 533 |  | $ | 2,220 |
In 2010, all benefit and service accruals for nonunion and certain union plans were frozen. In 2011 and effective September 30, 2012, all benefit and service accruals for certain additional union employees were frozen. These employees are eligible to receive additional defined contribution plan benefits. In addition to the qualified plan defined pension benefits reflected in the table, the Company has unfunded, nonqualified benefit plans for executive officers and certain key management employees that generally provide for defined benefit payments at age 65 following the employee's retirement or to their beneficiaries upon death for a 15-year period. The Company's net periodic benefit cost for this plan for the three and six months ended June 30, 2013, was $1.8 million and $3.6 million, respectively. The company's net periodic benefit cost for this plan for the three and six months ended June 30, 2012, was $2.0 million and $4.1 million, respectively. In 2012, the Company modified health care coverage for certain retirees. Effective January 1, 2013, post-65 coverage is replaced by a fixed-dollar subsidy for certain retirees and spouses to be used to purchase individual insurance through an exchange.

X
- Details
Name: | mdu_EmployeeBenefitPlansAbstract
Namespace Prefix: | mdu_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition The entire disclosure for pension and other postretirement benefits. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -URI http://asc.fasb.org/topic&trid=2235017 + Details
Name: | us-gaap_PensionAndOtherPostretirementBenefitsDisclosureTextBlock
Namespace Prefix: | us-gaap_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration