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Summary of significant accounting policies (Tables) | 12 Months Ended
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Dec. 31, 2012
Accounting Policies [Abstract] |
Inventories | Inventories at December 31 consisted of:
| 2012 |  | 2011 |
| (In thousands)
Aggregates held for resale | $ | 87,715 |  | $ | 78,518 |
Materials and supplies | 69,390 |  | 61,611 |
Natural gas in storage (current) | 29,030 |  | 36,578 |
Asphalt oil | 67,480 |  | 32,335 |
Merchandise for resale | 31,172 |  | 32,165 |
Other | 32,628 |  | 32,998 |
Total | $ | 317,415 |  | $ | 274,205 |
AFUDC and interest capitailized | The amount of AFUDC and interest capitalized for the years ended December 31 were as follows:
| 2012 |  | 2011 |  | 2010 |
| (In thousands)
Interest capitalized | $ | 8,659 |  | $ | 10,821 |  | $ | 9,753 |
AFUDC - borrowed | $ | 2,483 |  | $ | 1,666 |  | $ | 2,950 |
AFUDC - equity | $ | 4,530 |  | $ | 2,587 |  | $ | 4,896 |
Property, plant and equipment | Property, plant and equipment at December 31 was as follows:
| 2012 |  | 2011 |  | Weighted Average Depreciable Life in Years
| (Dollars in thousands, where applicable)
Regulated: |  |  |
Electric: |  |  |
Generation | $ | 580,567 |  | $ | 546,783 |  | 47
Distribution | 282,424 |  | 255,232 |  | 36
Transmission | 190,311 |  | 179,580 |  | 44
Other | 97,282 |  | 86,929 |  | 14
Natural gas distribution: |  |  |  |  |
Distribution | 1,329,692 |  | 1,257,360 |  | 40
Other | 360,258 |  | 311,506 |  | 24
Pipeline and energy services: |  |  |  |  |
Transmission | 416,186 |  | 386,227 |  | 52
Gathering | 42,424 |  | 42,378 |  | 19
Storage | 42,554 |  | 41,908 |  | 51
Other | 38,493 |  | 36,179 |  | 29
Nonregulated: |  |  |  |  |
Pipeline and energy services: |  |  |  |  |
Gathering | 259,724 |  | 198,864 |  | 16
Other | 17,152 |  | 13,735 |  | 10
Exploration and production: |  |  |  |  |
Oil and natural gas properties | 2,723,356 |  | 2,577,576 |  | *
Other | 41,204 |  | 37,570 |  | 8
Construction materials and contracting: |  |  |  |  |
Land | 126,788 |  | 126,790 |  | -
Buildings and improvements | 73,884 |  | 67,627 |  | 19
Machinery, vehicles and equipment | 899,592 |  | 902,136 |  | 12
Construction in progress | 11,165 |  | 8,085 |  | -
Aggregate reserves | 393,552 |  | 395,214 |  | **
Construction services: |  |  |  |  |
Land | 4,723 |  | 4,706 |  | -
Buildings and improvements | 16,563 |  | 15,001 |  | 23
Machinery, vehicles and equipment | 100,445 |  | 95,891 |  | 7
Other | 8,893 |  | 9,198 |  | 4
Other: |  |  |  |  |
Land | 2,837 |  | 2,837 |  | -
Other | 47,682 |  | 46,910 |  | 24
Less accumulated depreciation, depletion and amortization | 3,608,912 |  | 3,361,208 |  |
Net property, plant and equipment | $ | 4,498,839 |  | $ | 4,285,014 |  |
* Amortized on the units-of-production method based on total proved reserves at a BOE average rate of $15.28, $12.25 and $10.64 for the years ended December 31, 2012, 2011 and 2010, respectively. Includes oil and natural gas properties accounted for under the full-cost method, of which $191.8 million and $232.5 million were excluded from amortization at December 31, 2012 and 2011, respectively. ** Depleted on the units-of-production method.
Summary of natural gas and oil properties not subject to amortization | The following table summarizes the Company's oil and natural gas properties not subject to amortization at December 31, 2012, in total and by the year in which such costs were incurred:
|  | Year Costs Incurred
| Total |  | 2012 |  | 2011 |  | 2010 |  | 2009 and prior |
| (In thousands)
Acquisition | $ | 144,521 |  | $ | 26,318 |  | $ | 38,186 |  | $ | 22,142 |  | $ | 57,875 |
Development | 7,415 |  | 6,858 |  | 399 |  | 77 |  | 81 |
Exploration | 36,246 |  | 34,407 |  | 856 |  | 643 |  | 340 |
Capitalized interest | 3,612 |  | 1,297 |  | 757 |  | 439 |  | 1,119 |
Total costs not subject to amortization | $ | 191,794 |  | $ | 68,880 |  | $ | 40,198 |  | $ | 23,301 |  | $ | 59,415 |
Schedule of earnings per share reconciliation | Net income (loss) was the same for both the basic and diluted earnings (loss) per share calculations. A reconciliation of the weighted average common shares outstanding used in the basic and diluted earnings (loss) per share calculation was as follows:
| 2012 |  | 2011 |  | 2010 |
| (In thousands)
Weighted average common shares outstanding - basic | 188,826 |  | 188,763 |  | 188,137 |
Effect of dilutive stock options and performance share awards | — |  | 142 |  | 92 |
Weighted average common shares outstanding - diluted | 188,826 |  | 188,905 |  | 188,229 |
Shares excluded from the calculation of diluted earnings per share | 58 |  | — |  | — |
Cash expenditures for interest and income taxes and noncash investing transactions | Cash expenditures for interest and income taxes for the years ended December 31 were as follows:
| 2012 |  | 2011 |  | 2010 |
| (In thousands)
Interest, net of amount capitalized | $ | 74,378 |  | $ | 78,133 |  | $ | 80,962 |
Income taxes paid (refunded), net | $ | 3,277 |  | $ | (12,287 | ) | $ | 46,892 |
Noncash investing transactions at December 31 were as follows:
| 2012 |  | 2011 |  | 2010 |
| (In thousands)
Property, plant and equipment additions in accounts payable | $ | 76,205 |  | $ | 41,540 |  | $ | 30,895 |
After-tax components of accumulated other comprehensive income (loss) | The after-tax components of accumulated other comprehensive loss as of December 31, 2012, 2011 and 2010, were as follows:
| Net Unrealized Gain (Loss) on Derivative Instruments Qualifying as Hedges |  | Postretirement Liability Adjustment |  | Foreign Currency Translation Adjustment |  | Net Unrealized Gains on Available-for-sale Investments |  | Total Accumulated Other Comprehensive Loss |
| (In thousands)
Balance at December 31, 2010 | $ | (1,625 | ) | $ | (30,893 | ) | $ | 1,257 |  | $ | — |  | $ | (31,261 | )
Current-period other comprehensive loss | 7,900 |  | (22,427 | ) | (1,295 | ) | 82 |  | (15,740 | )
Balance at December 31, 2011 | 6,275 |  | (53,320 | ) | (38 | ) | 82 |  | (47,001 | )
Current-period other comprehensive loss | (257 | ) | (1,027 | ) | (473 | ) | 37 |  | (1,720 | )
Balance at December 31, 2012 | $ | 6,018 |  | $ | (54,347 | ) | $ | (511 | ) | $ | 119 |  | $ | (48,721 | )

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- Definition Tabular disclosure of the useful life and salvage value of long-lived, physical assets that are used in the normal conduct of business to produce goods and services and not intended for resale. Examples include land, buildings, machinery and equipment, and other types of furniture and equipment including, but not limited to, office equipment, furniture and fixtures, and computer equipment and software. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 13 -Subparagraph b -Article 5 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Principles Board Opinion (APB) -Number 12 -Paragraph 5 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. Reference 3: 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 Reference 4: 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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