Document_and_Entity_Informatio
Document and Entity Information | 3 Months Ended | |
Mar. 31, 2014 | Apr. 28, 2014 | |
Document And Entity Information [Abstract] | ' | ' |
Document Type | '10-Q | ' |
Amendment Flag | 'false | ' |
Document Period End Date | 31-Mar-14 | ' |
Document Fiscal Year Focus | '2014 | ' |
Document Fiscal Period Focus | 'Q1 | ' |
Trading Symbol | 'SWX | ' |
Entity Registrant Name | 'SOUTHWEST GAS CORP | ' |
Entity Central Index Key | '0000092416 | ' |
Current Fiscal Year End Date | '--12-31 | ' |
Entity Filer Category | 'Large Accelerated Filer | ' |
Entity Common Stock, Shares Outstanding | ' | 46,503,111 |
Condensed_Consolidated_Balance
Condensed Consolidated Balance Sheets (USD $) | Mar. 31, 2014 | Dec. 31, 2013 |
In Thousands, unless otherwise specified | ||
Utility plant: | ' | ' |
Gas plant | $5,341,734 | $5,252,469 |
Less: accumulated depreciation | -1,900,044 | -1,868,504 |
Acquisition adjustments, net | 685 | 730 |
Construction work in progress | 70,285 | 101,413 |
Net utility plant | 3,512,660 | 3,486,108 |
Other property and investments | 262,187 | 260,871 |
Current assets: | ' | ' |
Cash and cash equivalents | 85,366 | 41,077 |
Accounts receivable, net of allowances | 205,511 | 219,469 |
Accrued utility revenue | 44,100 | 72,700 |
Income taxes receivable, net | ' | 3,790 |
Deferred income taxes | 4,979 | 31,130 |
Deferred purchased gas costs | 75,196 | 18,217 |
Prepaids and other current assets | 84,661 | 108,289 |
Total current assets | 499,813 | 494,672 |
Deferred charges and other assets | 326,147 | 323,523 |
Total assets | 4,600,807 | 4,565,174 |
Capitalization: | ' | ' |
Common stock, $1 par (authorized- 60,000,000 shares; issued and outstanding- 46,495,191 and 46,356,125 shares) | 48,125 | 47,986 |
Additional paid-in capital | 843,463 | 840,521 |
Accumulated other comprehensive income (loss), net | -40,668 | -41,698 |
Retained earnings | 621,304 | 567,714 |
Total Southwest Gas Corporation equity | 1,472,224 | 1,414,523 |
Noncontrolling interest | -2,214 | -2,128 |
Total equity | 1,470,010 | 1,412,395 |
Long-term debt, less current maturities | 1,368,632 | 1,381,327 |
Total capitalization | 2,838,642 | 2,793,722 |
Current liabilities: | ' | ' |
Current maturities of long-term debt | 11,158 | 11,105 |
Accounts payable | 122,212 | 183,511 |
Customer deposits | 73,669 | 73,367 |
Income taxes payable | 14,588 | ' |
Accrued general taxes | 54,743 | 39,681 |
Accrued interest | 23,563 | 17,920 |
Other current liabilities | 117,141 | 108,580 |
Total current liabilities | 417,074 | 434,164 |
Deferred income taxes and other credits: | ' | ' |
Deferred income taxes and investment tax credits | 662,583 | 674,411 |
Taxes payable | 244 | 284 |
Accumulated removal costs | 285,000 | 279,000 |
Other deferred credits | 397,264 | 383,593 |
Total deferred income taxes and other credits | 1,345,091 | 1,337,288 |
Total capitalization and liabilities | $4,600,807 | $4,565,174 |
Condensed_Consolidated_Balance1
Condensed Consolidated Balance Sheets (Parenthetical) (USD $) | Mar. 31, 2014 | Dec. 31, 2013 |
Statement Of Financial Position [Abstract] | ' | ' |
Common stock, par | $1 | $1 |
Common stock, authorized | 60,000,000 | 60,000,000 |
Common stock, issued | 46,495,191 | 46,356,125 |
Common stock, outstanding | 46,495,191 | 46,356,125 |
Condensed_Consolidated_Stateme
Condensed Consolidated Statements of Income (USD $) | 3 Months Ended | 12 Months Ended | ||
In Thousands, except Per Share data, unless otherwise specified | Mar. 31, 2014 | Mar. 31, 2013 | Mar. 31, 2014 | Mar. 31, 2013 |
Operating revenues: | ' | ' | ' | ' |
Gas operating revenues | $486,493 | $493,600 | $1,293,047 | $1,284,615 |
Construction revenues | 121,903 | 119,905 | 652,626 | 599,023 |
Total operating revenues | 608,396 | 613,505 | 1,945,673 | 1,883,638 |
Operating expenses: | ' | ' | ' | ' |
Net cost of gas sold | 191,377 | 200,608 | 426,770 | 437,463 |
Operations and maintenance | 102,408 | 97,087 | 390,235 | 371,216 |
Depreciation and amortization | 62,891 | 58,933 | 240,775 | 228,192 |
Taxes other than income taxes | 11,456 | 11,795 | 45,212 | 42,792 |
Construction expenses | 113,199 | 106,688 | 579,795 | 528,680 |
Total operating expenses | 481,331 | 475,111 | 1,682,787 | 1,608,343 |
Operating income | 127,065 | 138,394 | 262,886 | 275,295 |
Other income and (expenses): | ' | ' | ' | ' |
Net interest deductions | -17,519 | -15,878 | -65,341 | -66,739 |
Other income (deductions) | 1,612 | 4,069 | 9,843 | 3,052 |
Total other income and (expenses) | -15,907 | -11,809 | -55,498 | -63,687 |
Income before income taxes | 111,158 | 126,585 | 207,388 | 211,608 |
Income tax expense | 40,461 | 45,911 | 72,492 | 77,130 |
Net income | 70,697 | 80,674 | 134,896 | 134,478 |
Net income (loss) attributable to noncontrolling interest | -86 | -99 | -434 | -707 |
Net income attributable to Southwest Gas Corporation | $70,783 | $80,773 | $135,330 | $135,185 |
Basic earnings per share | $1.52 | $1.75 | $2.92 | $2.93 |
Diluted earnings per share | $1.51 | $1.73 | $2.89 | $2.90 |
Dividends declared per share | $0.37 | $0.33 | $1.36 | $1.22 |
Average number of common shares outstanding | 46,440 | 46,251 | 46,364 | 46,160 |
Average shares outstanding (assuming dilution) | 46,871 | 46,650 | 46,812 | 46,600 |
Condensed_Consolidated_Stateme1
Condensed Consolidated Statements of Comprehensive Income (USD $) | 3 Months Ended | 12 Months Ended | ||
In Thousands, unless otherwise specified | Mar. 31, 2014 | Mar. 31, 2013 | Mar. 31, 2014 | Mar. 31, 2013 |
Statement Of Income And Comprehensive Income [Abstract] | ' | ' | ' | ' |
Net income | $70,697 | $80,674 | $134,896 | $134,478 |
Defined benefit pension plans: | ' | ' | ' | ' |
Net actuarial gain (loss) | ' | ' | 62,214 | -46,409 |
Amortization of prior service cost | 55 | 55 | 220 | 55 |
Amortization of transition obligation | ' | ' | ' | 404 |
Amortization of net actuarial loss | 3,667 | 5,298 | 19,559 | 17,200 |
Prior service cost | ' | ' | ' | -1,502 |
Regulatory adjustment | -3,210 | -4,702 | -75,159 | 25,442 |
Net defined benefit pension plans | 512 | 651 | 6,834 | -4,810 |
Forward-starting interest rate swaps: | ' | ' | ' | ' |
Amounts reclassified into net income | 518 | 518 | 2,074 | 2,074 |
Net forward-starting interest rate swaps | 518 | 518 | 2,074 | 2,074 |
Total other comprehensive income (loss), net of tax | 1,030 | 1,169 | 8,908 | -2,736 |
Comprehensive income | 71,727 | 81,843 | 143,804 | 131,742 |
Comprehensive income (loss) attributable to noncontrolling interest | -86 | -99 | -434 | -707 |
Comprehensive income attributable to Southwest Gas Corporation | $71,813 | $81,942 | $144,238 | $132,449 |
Condensed_Consolidated_Stateme2
Condensed Consolidated Statements of Cash Flows (USD $) | 3 Months Ended | 12 Months Ended | ||
In Thousands, unless otherwise specified | Mar. 31, 2014 | Mar. 31, 2013 | Mar. 31, 2014 | Mar. 31, 2013 |
CASH FLOW FROM OPERATING ACTIVITIES: | ' | ' | ' | ' |
Net income | $70,697 | $80,674 | $134,896 | $134,478 |
Adjustments to reconcile net income to net cash provided by operating activities: | ' | ' | ' | ' |
Depreciation and amortization | 62,891 | 58,933 | 240,775 | 228,192 |
Deferred income taxes | 13,692 | 40,241 | 42,090 | 66,983 |
Changes in current assets and liabilities: | ' | ' | ' | ' |
Accounts receivable, net of allowances | 13,958 | -11,404 | 2,806 | 2,418 |
Accrued utility revenue | 28,600 | 28,400 | -500 | 100 |
Deferred purchased gas costs | -56,979 | -51,444 | -116,678 | -34,233 |
Accounts payable | -66,641 | -37,931 | -1,042 | -7,844 |
Accrued taxes | 33,400 | 20,733 | 13,592 | -1,042 |
Other current assets and liabilities | 36,522 | 34,141 | 7,465 | -21,220 |
Gains on sale | -2,429 | -834 | -5,707 | -7,460 |
Changes in undistributed stock compensation | 2,761 | 2,659 | 7,060 | 6,695 |
AFUDC and property-related changes | -498 | -471 | -2,301 | -2,092 |
Changes in other assets and deferred charges | -11,134 | -11,859 | -20,994 | -11,168 |
Changes in other liabilities and deferred credits | 17,155 | -18,237 | 53,141 | -255 |
Net cash provided by operating activities | 141,995 | 133,601 | 354,603 | 353,552 |
CASH FLOW FROM INVESTING ACTIVITIES: | ' | ' | ' | ' |
Construction expenditures and property additions | -76,892 | -53,237 | -387,931 | -363,984 |
Changes in customer advances | 4,105 | 906 | 10,972 | 4,434 |
Miscellaneous inflows | 3,593 | 1,600 | 10,458 | 13,299 |
Miscellaneous outflows | ' | ' | ' | -2,004 |
Net cash used in investing activities | -69,194 | -50,731 | -366,501 | -348,255 |
CASH FLOW FROM FINANCING ACTIVITIES: | ' | ' | ' | ' |
Issuance of common stock, net | 107 | 1,175 | 567 | 2,024 |
Dividends paid | -15,343 | -13,658 | -61,220 | -54,483 |
Issuance of long-term debt, net | 1,025 | 4,664 | 307,651 | 168,304 |
Retirement of long-term debt | -3,781 | -69,500 | -71,294 | -419,121 |
Change in credit facility and commercial paper | -10,000 | 2,000 | -113,000 | 113,000 |
Other | -520 | ' | 1,479 | ' |
Net cash provided by (used in) financing activities | -28,512 | -75,319 | 64,183 | -190,276 |
Change in cash and cash equivalents | 44,289 | 7,551 | 52,285 | -184,979 |
Cash and cash equivalents at beginning of period | 41,077 | 25,530 | 33,081 | 218,060 |
Cash and cash equivalents at end of period | 85,366 | 33,081 | 85,366 | 33,081 |
Supplemental information: | ' | ' | ' | ' |
Interest paid, net of amounts capitalized | 10,474 | 13,146 | 56,058 | 63,339 |
Income taxes paid | $238 | $634 | $6,454 | $4,666 |
Nature_of_Operations_and_Basis
Nature of Operations and Basis of Presentation | 3 Months Ended | ||||||||||||||||
Mar. 31, 2014 | |||||||||||||||||
Accounting Policies [Abstract] | ' | ||||||||||||||||
Nature of Operations and Basis of Presentation | ' | ||||||||||||||||
Note 1 – Nature of Operations and Basis of Presentation | |||||||||||||||||
Nature of Operations. Southwest Gas Corporation and its subsidiaries (the “Company”) consist of two segments: natural gas operations (“Southwest” or the “natural gas operations” segment) and construction services. Southwest is engaged in the business of purchasing, distributing, and transporting natural gas for customers in portions of Arizona, Nevada, and California. Public utility rates, practices, facilities, and service territories of Southwest are subject to regulatory oversight. The timing and amount of rate relief can materially impact results of operations. Natural gas sales are seasonal, peaking during the winter months; therefore, results of operations for interim periods are not necessarily indicative of results for a full year. Natural gas purchases and the timing of related recoveries can materially impact liquidity. NPL Construction Co. (“NPL” or the “construction services” segment), a wholly owned subsidiary, is a full-service underground piping contractor that primarily provides utility companies with trenching and installation, replacement, and maintenance services for energy distribution systems. Typically, NPL revenues are lowest during the first quarter of the year due to unfavorable winter weather conditions. Operating revenues typically improve as more favorable weather conditions occur during the summer and fall months. | |||||||||||||||||
Basis of Presentation. The condensed consolidated financial statements included herein have been prepared by the Company, without audit, pursuant to the rules and regulations of the Securities and Exchange Commission (the “SEC”). Certain information and footnote disclosures normally included in financial statements prepared in accordance with generally accepted accounting principles (“GAAP”) have been condensed or omitted pursuant to such rules and regulations. The preparation of the condensed consolidated financial statements requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements, and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. In the opinion of management, all adjustments, consisting of normal recurring items and estimates necessary for a fair presentation of results for the interim periods, have been made. It is suggested that these condensed consolidated financial statements be read in conjunction with the consolidated financial statements and the notes thereto included in the 2013 Annual Report to Shareholders, which is incorporated by reference into the 2013 Form 10-K. | |||||||||||||||||
Prepaids and other current assets. Prepaids and other current assets includes gas pipe inventory and operating supplies of $21 million at both March 31, 2014 and December 31, 2013. | |||||||||||||||||
Cash and Cash Equivalents. For purposes of reporting consolidated cash flows, cash and cash equivalents include cash on hand and financial instruments with a purchase-date maturity of three months or less. Cash and cash equivalents fall within Level 1 (quoted prices for identical financial instruments) of the three-level fair value hierarchy that ranks the inputs used to measure fair value by their reliability. Upon contract expiration, customer advances of approximately $1.6 million and $2.8 million, during the first quarters of 2014 and 2013, respectively, were applied as contributions toward utility construction activity and represent non-cash investing activity. | |||||||||||||||||
Intercompany Transactions. NPL recognizes revenues generated from contracts with Southwest (see Note 3—Segment Information below). Accounts receivable for these services are presented in the table below (thousands of dollars): | |||||||||||||||||
March 31, 2014 | December 31, 2013 | ||||||||||||||||
Accounts receivable for NPL services | $ | 7,245 | $ | 10,787 | |||||||||||||
The accounts receivable balance, revenues, and associated profits are included in the condensed consolidated financial statements of the Company and were not eliminated during consolidation in accordance with accounting treatment for rate-regulated entities. | |||||||||||||||||
Other Property and Investments. Other property and investments includes (millions of dollars): | |||||||||||||||||
March 31, 2014 | December 31, 2013 | ||||||||||||||||
NPL property and equipment | $ | 325 | $ | 320 | |||||||||||||
NPL accumulated provision for depreciation and amortization | (168 | ) | (163 | ) | |||||||||||||
Net cash surrender value of COLI policies | 94 | 93 | |||||||||||||||
Other property | 11 | 11 | |||||||||||||||
Total | $ | 262 | $ | 261 | |||||||||||||
Other Income (Deductions). The following table provides the composition of significant items included in Other income (deductions) in the condensed consolidated statements of income (thousands of dollars): | |||||||||||||||||
Three Months Ended | Twelve Months Ended | ||||||||||||||||
March 31 | March 31 | ||||||||||||||||
2014 | 2013 | 2014 | 2013 | ||||||||||||||
Change in COLI policies | $ | 900 | $ | 3,800 | $ | 9,500 | $ | 5,200 | |||||||||
Interest income | 497 | 120 | 838 | 818 | |||||||||||||
Pipe replacement costs | — | (85 | ) | (47 | ) | (2,756 | ) | ||||||||||
Miscellaneous income and (expense) | 215 | 234 | (448 | ) | (210 | ) | |||||||||||
Total other income (deductions) | $ | 1,612 | $ | 4,069 | $ | 9,843 | $ | 3,052 | |||||||||
Included in the table above is the change in cash surrender values of company-owned life insurance (“COLI”) policies (including net death benefits recognized). These life insurance policies on members of management and other key employees are used by Southwest to indemnify itself against the loss of talent, expertise, and knowledge, as well as to provide indirect funding for certain nonqualified benefit plans. Current tax regulations provide for tax-free treatment of life insurance (death benefit) proceeds. Therefore, changes in the cash surrender value components of COLI policies, as they progress towards the ultimate death benefits, are also recorded without tax consequences. Pipe replacement costs include amounts associated with certain Arizona non-recoverable pipe replacement work. The replacement program work subject to non-recoverability was substantially completed in 2012. | |||||||||||||||||
Reclassifications. A reclassification was made to the prior year’s financial information between two categories on the Condensed Consolidated Statements of Comprehensive Income to present it on a basis comparable with the current year’s presentation, with no impact on comprehensive income overall. |
Components_of_Net_Periodic_Ben
Components of Net Periodic Benefit Cost | 3 Months Ended | ||||||||||||||||
Mar. 31, 2014 | |||||||||||||||||
Text Block [Abstract] | ' | ||||||||||||||||
Components of Net Periodic Benefit Cost | ' | ||||||||||||||||
Note 2 – Components of Net Periodic Benefit Cost | |||||||||||||||||
Southwest has a noncontributory qualified retirement plan with defined benefits covering substantially all employees and a separate unfunded supplemental retirement plan (“SERP”) which is limited to officers. Southwest also provides postretirement benefits other than pensions (“PBOP”) to its qualified retirees for health care, dental, and life insurance. | |||||||||||||||||
Net periodic benefit costs included in the table below are components of an overhead loading process associated with the cost of labor. The overhead process ultimately results in allocation of net periodic benefit costs to the same accounts to which productive labor is charged. As a result, net periodic benefit costs become components of various accounts, primarily operations and maintenance expense, net utility plant, and deferred charges and other assets. | |||||||||||||||||
Qualified Retirement Plan | |||||||||||||||||
Period Ended March 31, | |||||||||||||||||
Three Months | Twelve Months | ||||||||||||||||
(Thousands of dollars) | 2014 | 2013 | 2014 | 2013 | |||||||||||||
Service cost | $ | 5,340 | $ | 5,764 | $ | 22,632 | $ | 21,004 | |||||||||
Interest cost | 10,861 | 9,401 | 39,067 | 38,100 | |||||||||||||
Expected return on plan assets | (13,336 | ) | (12,460 | ) | (50,716 | ) | (46,795 | ) | |||||||||
Amortization of net actuarial loss | 5,718 | 8,066 | 29,913 | 25,978 | |||||||||||||
Net periodic benefit cost | $ | 8,583 | $ | 10,771 | $ | 40,896 | $ | 38,287 | |||||||||
SERP | |||||||||||||||||
Period Ended March 31, | |||||||||||||||||
Three Months | Twelve Months | ||||||||||||||||
(Thousands of dollars) | 2014 | 2013 | 2014 | 2013 | |||||||||||||
Service cost | $ | 73 | $ | 94 | $ | 352 | $ | 299 | |||||||||
Interest cost | 436 | 383 | 1,588 | 1,605 | |||||||||||||
Amortization of net actuarial loss | 196 | 243 | 924 | 755 | |||||||||||||
Net periodic benefit cost | $ | 705 | $ | 720 | $ | 2,864 | $ | 2,659 | |||||||||
PBOP | |||||||||||||||||
Period Ended March 31, | |||||||||||||||||
Three Months | Twelve Months | ||||||||||||||||
(Thousands of dollars) | 2014 | 2013 | 2014 | 2013 | |||||||||||||
Service cost | $ | 276 | $ | 305 | $ | 1,191 | $ | 1,037 | |||||||||
Interest cost | 707 | 620 | 2,569 | 2,531 | |||||||||||||
Expected return on plan assets | (816 | ) | (706 | ) | (2,934 | ) | (2,509 | ) | |||||||||
Amortization of prior service cost | 89 | 89 | 355 | 89 | |||||||||||||
Amortization of transition obligation | — | — | — | 650 | |||||||||||||
Amortization of net actuarial loss | — | 236 | 709 | 1,009 | |||||||||||||
Net periodic benefit cost | $ | 256 | $ | 544 | $ | 1,890 | $ | 2,807 |
Segment_Information
Segment Information | 3 Months Ended | ||||||||||||
Mar. 31, 2014 | |||||||||||||
Segment Reporting [Abstract] | ' | ||||||||||||
Segment Information | ' | ||||||||||||
Note 3 – Segment Information | |||||||||||||
The following tables present revenues from external customers, intersegment revenues, and segment net income (thousands of dollars): | |||||||||||||
Natural Gas | Construction | Total | |||||||||||
Operations | Services | ||||||||||||
Three months ended March 31, 2014 | |||||||||||||
Revenues from external customers | $ | 486,493 | $ | 98,153 | $ | 584,646 | |||||||
Intersegment revenues | — | 23,750 | 23,750 | ||||||||||
Total | $ | 486,493 | $ | 121,903 | $ | 608,396 | |||||||
Segment net income (loss) | $ | 72,599 | $ | (1,816 | ) | $ | 70,783 | ||||||
Three months ended March 31, 2013 | |||||||||||||
Revenues from external customers | $ | 493,600 | $ | 104,866 | $ | 598,466 | |||||||
Intersegment revenues | — | 15,039 | 15,039 | ||||||||||
Total | $ | 493,600 | $ | 119,905 | $ | 613,505 | |||||||
Segment net income | $ | 79,292 | $ | 1,481 | $ | 80,773 | |||||||
Natural Gas | Construction | Total | |||||||||||
Operations | Services | ||||||||||||
Twelve months ended March 31, 2014 | |||||||||||||
Revenues from external customers | $ | 1,293,047 | $ | 555,762 | $ | 1,848,809 | |||||||
Intersegment revenues | — | 96,864 | 96,864 | ||||||||||
Total | $ | 1,293,047 | $ | 652,626 | $ | 1,945,673 | |||||||
Segment net income | $ | 117,476 | $ | 17,854 | $ | 135,330 | |||||||
Twelve months ended March 31, 2013 | |||||||||||||
Revenues from external customers | $ | 1,284,615 | $ | 516,655 | $ | 1,801,270 | |||||||
Intersegment revenues | — | 82,368 | 82,368 | ||||||||||
Total | $ | 1,284,615 | $ | 599,023 | $ | 1,883,638 | |||||||
Segment net income | $ | 116,545 | $ | 18,640 | $ | 135,185 |
Derivatives_and_Fair_Value_Mea
Derivatives and Fair Value Measurements | 3 Months Ended | ||||||||||||||||||
Mar. 31, 2014 | |||||||||||||||||||
Derivative Instruments And Hedging Activities Disclosure [Abstract] | ' | ||||||||||||||||||
Derivatives and Fair Value Measurements | ' | ||||||||||||||||||
Note 4 – Derivatives and Fair Value Measurements | |||||||||||||||||||
Derivatives. In managing its natural gas supply portfolios, Southwest has historically entered into fixed- and variable-price contracts, which qualify as derivatives. Additionally, Southwest utilizes fixed-for-floating swap contracts (“Swaps”) to supplement its fixed-price contracts. The fixed-price contracts, firm commitments to purchase a fixed amount of gas in the future at a fixed price, qualify for the normal purchases and normal sales exception that is allowed for contracts that are probable of delivery in the normal course of business, and are exempt from fair value reporting. The variable-price contracts have no significant market value. The Swaps are recorded at fair value. | |||||||||||||||||||
As part of the June 2013 Nevada Annual Rate Adjustment and associated stipulation, the Company agreed to suspend further Swaps and fixed-price purchases pursuant to the Volatility Mitigation Program for its Nevada service territories. The decision will not impact previously executed purchase agreements. The Company, along with its regulators, will continue to evaluate this strategy in light of prevailing or anticipated changing market conditions. | |||||||||||||||||||
The fixed-price contracts and Swaps are utilized by Southwest under its volatility mitigation programs to effectively fix the price on a portion (up to 35%, depending on the jurisdiction) of its natural gas supply portfolios. The maturities of the Swaps highly correlate to forecasted purchases of natural gas, during time frames ranging from April 2014 through March 2016. Under such contracts, Southwest pays the counterparty at a fixed rate and receives from the counterparty a floating rate per MMBtu (“dekatherm”) of natural gas. Only the net differential is actually paid or received. The differential is calculated based on the notional amounts under the contracts, which are detailed in the table below (thousands of dekatherms): | |||||||||||||||||||
March 31, 2014 | December 31, 2013 | ||||||||||||||||||
Contract notional amounts | 7,664 | 13,571 | |||||||||||||||||
Southwest does not utilize derivative financial instruments for speculative purposes, nor does it have trading operations. | |||||||||||||||||||
The following table sets forth the gains and (losses) recognized on the Company’s Swaps (derivatives) for the three-and twelve-month periods ended March 31, 2014 and 2013 and their location in the Condensed Consolidated Statements of Income (thousands of dollars): | |||||||||||||||||||
Gains (losses) recognized in income for derivatives not designated as hedging instruments: | |||||||||||||||||||
(Thousands of dollars) | |||||||||||||||||||
Location of Gain or (Loss) | Three Months Ended | Twelve Months Ended | |||||||||||||||||
Recognized in Income on Derivative | March 31 | March 31 | |||||||||||||||||
Instrument | 2014 | 2013 | 2014 | 2013 | |||||||||||||||
Swaps | Net cost of gas sold | $ | 5,990 | $ | 5,076 | $ | 1,890 | $ | 7,158 | ||||||||||
Swaps | Net cost of gas sold | (5,990 | )* | (5,076 | )* | (1,890 | )* | (7,158 | )* | ||||||||||
Total | $ | — | $ | — | $ | — | $ | — | |||||||||||
* | Represents the impact of regulatory deferral accounting treatment under U.S. GAAP for rate-regulated entities. | ||||||||||||||||||
No gains (losses) were recognized in income or other comprehensive income during the periods presented for derivatives designated as cash flow hedging instruments. Previously, Southwest entered into two forward-starting interest rate swaps (“FSIRS”) to hedge the risk of interest rate variability during the period leading up to the issuance of fixed-rate debt. At settlement of the first FSIRS in December 2010, Southwest paid an aggregate $11.7 million to the counterparties. The second FSIRS terminated in March 2012 at which time Southwest paid counterparties an aggregate $21.8 million. The losses on both FSIRS are being amortized over ten-year periods from Accumulated other comprehensive income (loss) and into interest expense. | |||||||||||||||||||
The following table sets forth the fair values of the Company’s Swaps and their location in the Condensed Consolidated Balance Sheets (thousands of dollars): | |||||||||||||||||||
Fair values of derivatives not designated as hedging instruments: | |||||||||||||||||||
March 31, 2014 | Balance Sheet Location | Asset | Liability | Net Total | |||||||||||||||
Instrument | Derivatives | Derivatives | |||||||||||||||||
Swaps | Deferred charges and other assets | $ | 352 | $ | (16 | ) | $ | 336 | |||||||||||
Swaps | Prepaids and other current assets | 2,171 | — | 2,171 | |||||||||||||||
Total | $ | 2,523 | $ | (16 | ) | $ | 2,507 | ||||||||||||
31-Dec-13 | Balance Sheet Location | Asset | Liability | Net Total | |||||||||||||||
Instrument | Derivatives | Derivatives | |||||||||||||||||
Swaps | Deferred charges and other assets | $ | 257 | $ | (77 | ) | $ | 180 | |||||||||||
Swaps | Prepaids and other current assets | 1,054 | (253 | ) | 801 | ||||||||||||||
Swaps | Other current liabilities | 126 | (282 | ) | (156 | ) | |||||||||||||
Swaps | Other deferred credits | 7 | (11 | ) | (4 | ) | |||||||||||||
Total | $ | 1,444 | $ | (623 | ) | $ | 821 | ||||||||||||
The estimated fair values of the natural gas derivatives were determined using future natural gas index prices (as more fully described below). The Company has master netting arrangements with each counterparty that provide for the net settlement of all contracts through a single payment. As applicable, the Company has elected to reflect the net amounts in its balance sheets. The Company had no outstanding collateral associated with the Swaps during either period shown in the above table. | |||||||||||||||||||
Pursuant to regulatory deferral accounting treatment for rate-regulated entities, Southwest records the unrealized gains and losses in fair value of the Swaps as a regulatory asset and/or liability. When the Swaps mature, Southwest reverses any prior positions held and records the settled position as an increase or decrease of purchased gas under the related purchased gas adjustment (“PGA”) mechanism in determining its deferred PGA balances. Neither changes in fair value, nor settled amounts, of Swaps have a direct effect on earnings or other comprehensive income. | |||||||||||||||||||
The following table shows the amounts Southwest paid to and received from counterparties for settlements of matured Swaps. | |||||||||||||||||||
(Thousands of dollars) | Three Months Ended | Twelve Months Ended | |||||||||||||||||
March 31, 2014 | March 31, 2014 | ||||||||||||||||||
Paid to counterparties | $ | 15 | $ | 2,294 | |||||||||||||||
Received from counterparties | $ | 4,319 | $ | 4,869 | |||||||||||||||
The following table details the regulatory assets/(liabilities) offsetting the derivatives at fair value in the Condensed Consolidated Balance Sheets (thousands of dollars). | |||||||||||||||||||
March 31, 2014 | Balance Sheet Location | Net Total | |||||||||||||||||
Instrument | |||||||||||||||||||
Swaps | Other deferred credits | $ | (336 | ) | |||||||||||||||
Swaps | Other current liabilities | (2,171 | ) | ||||||||||||||||
31-Dec-13 | Balance Sheet Location | Net Total | |||||||||||||||||
Instrument | |||||||||||||||||||
Swaps | Other deferred credits | $ | (180 | ) | |||||||||||||||
Swaps | Other current liabilities | (801 | ) | ||||||||||||||||
Swaps | Prepaids and other current assets | 156 | |||||||||||||||||
Swaps | Deferred charges and other assets | 4 | |||||||||||||||||
Fair Value Measurements. The estimated fair values of Southwest’s Swaps were determined at March 31, 2014 and December 31, 2013 using New York Mercantile Exchange (“NYMEX”) futures settlement prices for delivery of natural gas at Henry Hub adjusted by the price of NYMEX ClearPort basis Swaps, which reflect the difference between the price of natural gas at a given delivery basin and the Henry Hub pricing points. These Level 2 inputs (inputs, other than quoted prices, for similar assets or liabilities) are observable in the marketplace throughout the full term of the Swaps, but have been credit-risk adjusted with no significant impact to the overall fair value measure. | |||||||||||||||||||
The following table sets forth by level within the three-level fair value hierarchy that ranks the inputs used to measure fair value by their reliability, the Company’s financial assets and liabilities recorded at fair value: | |||||||||||||||||||
Level 2 – Significant other observable inputs | |||||||||||||||||||
(Thousands of dollars) | March 31, 2014 | December 31, 2013 | |||||||||||||||||
Assets at fair value: | |||||||||||||||||||
Prepaids and other current assets—Swaps | $ | 2,171 | $ | 801 | |||||||||||||||
Deferred charges and other assets—Swaps | 336 | 180 | |||||||||||||||||
Liabilities at fair value: | |||||||||||||||||||
Other current liabilities—Swaps | — | (156 | ) | ||||||||||||||||
Other deferred credits—Swaps | — | (4 | ) | ||||||||||||||||
Net Assets (Liabilities) | $ | 2,507 | $ | 821 | |||||||||||||||
No financial assets or liabilities accounted for at fair value fell within Level 1 (quoted prices in active markets for identical financial assets) or Level 3 (significant unobservable inputs) of the fair value hierarchy. |
LongTerm_Debt
Long-Term Debt | 3 Months Ended | ||||||||||||||||
Mar. 31, 2014 | |||||||||||||||||
Debt Disclosure [Abstract] | ' | ||||||||||||||||
Long-Term Debt | ' | ||||||||||||||||
Note 5 – Long-Term Debt | |||||||||||||||||
Carrying amounts of the Company’s long-term debt and their related estimated fair values as of March 31, 2014 and December 31, 2013 are disclosed in the following table. The fair values of the revolving credit facility (including commercial paper), the NPL revolving credit facility, and the variable-rate Industrial Development Revenue Bonds (“IDRBs”) approximate their carrying values, and are categorized as Level 1 (quoted prices for identical financial instruments or liabilities that can be accessed at the measurement date) within the three-level fair value hierarchy that ranks the inputs used to measure fair value by their reliability. The market values of debentures (except the 6.1% Notes) and fixed-rate IDRBs are categorized as Level 2. The 6.1% Notes (private placement, not actively traded) and NPL other debt obligations (not actively traded) are categorized as Level 3 (based on significant unobservable inputs to their fair values). Fair values for the debentures, fixed-rate IDRBs, and NPL other debt obligations were determined through a market-based valuation approach, where fair market values are determined based on evaluated pricing data, such as broker quotes and yields for similar securities adjusted for observable differences. Significant inputs used in the valuation generally include benchmark yield curves and issuer spreads. The external credit rating, coupon rate, and maturity of each security are considered in the valuation, as applicable. | |||||||||||||||||
March 31, 2014 | December 31, 2013 | ||||||||||||||||
(Thousands of dollars) | Carrying | Market | Carrying | Market | |||||||||||||
Amount | Value | Amount | Value | ||||||||||||||
Debentures: | |||||||||||||||||
Notes, 4.45%, due 2020 | $ | 125,000 | $ | 134,433 | $ | 125,000 | $ | 130,953 | |||||||||
Notes, 6.1%, due 2041 | 125,000 | 148,894 | 125,000 | 141,873 | |||||||||||||
Notes, 3.875%, due 2022 | 250,000 | 255,923 | 250,000 | 252,485 | |||||||||||||
Notes, 4.875%, due 2043 | 250,000 | 268,873 | 250,000 | 257,280 | |||||||||||||
8% Series, due 2026 | 75,000 | 101,735 | 75,000 | 96,263 | |||||||||||||
Medium-term notes, 7.59% series, due 2017 | 25,000 | 28,691 | 25,000 | 28,741 | |||||||||||||
Medium-term notes, 7.78% series, due 2022 | 25,000 | 31,585 | 25,000 | 30,586 | |||||||||||||
Medium-term notes, 7.92% series, due 2027 | 25,000 | 33,402 | 25,000 | 31,497 | |||||||||||||
Medium-term notes, 6.76% series, due 2027 | 7,500 | 9,021 | 7,500 | 8,468 | |||||||||||||
Unamortized discount | (5,478 | ) | (5,560 | ) | |||||||||||||
902,022 | 901,940 | ||||||||||||||||
Revolving credit facility and commercial paper | — | — | 10,000 | 10,000 | |||||||||||||
Industrial development revenue bonds: | |||||||||||||||||
Variable-rate bonds: | |||||||||||||||||
Tax-exempt Series A, due 2028 | 50,000 | 50,000 | 50,000 | 50,000 | |||||||||||||
2003 Series A, due 2038 | 50,000 | 50,000 | 50,000 | 50,000 | |||||||||||||
2008 Series A, due 2038 | 50,000 | 50,000 | 50,000 | 50,000 | |||||||||||||
2009 Series A, due 2039 | 50,000 | 50,000 | 50,000 | 50,000 | |||||||||||||
Fixed-rate bonds: | |||||||||||||||||
5.25% 2003 Series D, due 2038 | 20,000 | 20,289 | 20,000 | 20,150 | |||||||||||||
5.25% 2004 Series A, due 2034 | 65,000 | 65,051 | 65,000 | 64,522 | |||||||||||||
5.00% 2004 Series B, due 2033 | 31,200 | 31,229 | 31,200 | 30,284 | |||||||||||||
4.85% 2005 Series A, due 2035 | 100,000 | 99,709 | 100,000 | 95,192 | |||||||||||||
4.75% 2006 Series A, due 2036 | 24,855 | 24,539 | 24,855 | 22,974 | |||||||||||||
Unamortized discount | (2,743 | ) | (2,776 | ) | |||||||||||||
438,312 | 438,279 | ||||||||||||||||
NPL credit facility | — | — | — | — | |||||||||||||
NPL other debt obligations | 39,456 | 39,465 | 42,213 | 42,119 | |||||||||||||
1,379,790 | 1,392,432 | ||||||||||||||||
Less: current maturities | (11,158 | ) | (11,105 | ) | |||||||||||||
Long-term debt, less current maturities | $ | 1,368,632 | $ | 1,381,327 | |||||||||||||
In March 2014, the Company amended its $300 million credit facility. The facility was previously scheduled to expire in March 2017 and was extended to March 2019. The Company will continue to use $150 million of the facility as long-term debt and the remaining $150 million for working capital purposes. In addition to extending the credit facility, among other amendments, the applicable margins and unused commitment fees were reduced and the Pricing Level definitions were modified. Interest rates for the credit facility are calculated at either the London Interbank Offered Rate (“LIBOR”) or an “alternate base rate,” plus in each case an applicable margin that is determined based on the Company’s senior unsecured debt rating. At March 31, 2014, the applicable margin is 1% for loans bearing interest with reference to LIBOR and 0% for loans bearing interest with reference to the alternative base rate. | |||||||||||||||||
Also in March 2014, the Company amended its 6.1% $125 million notes (“Notes”) note purchase agreement. The amendment modifies the Permitted Lien category permitting liens securing indebtedness not to exceed 10% of total capitalization as of the end of any quarter. This provision in the agreement prohibits liens on any property securing other indebtedness under bank facilities unless the Notes are secured in a similar manner. The provision was amended to clarify that it only applies to bank facilities of Southwest Gas Corporation. |
Equity_Other_Comprehensive_Inc
Equity, Other Comprehensive Income, and Accumulated Other Comprehensive Income | 3 Months Ended | ||||||||||||||||||||||||||||
Mar. 31, 2014 | |||||||||||||||||||||||||||||
Text Block [Abstract] | ' | ||||||||||||||||||||||||||||
Equity, Other Comprehensive Income, and Accumulated Other Comprehensive Income | ' | ||||||||||||||||||||||||||||
Note 6 – Equity, Other Comprehensive Income, and Accumulated Other Comprehensive Income | |||||||||||||||||||||||||||||
The table below provides details of activity in equity during the three months ended March 31, 2014. | |||||||||||||||||||||||||||||
Southwest Gas Corporation Equity | |||||||||||||||||||||||||||||
Common Stock | Additional | Accumulated | Retained | Non- | Total | ||||||||||||||||||||||||
Paid-in | Other | Earnings | controlling | ||||||||||||||||||||||||||
Capital | Comprehensive | Interest | |||||||||||||||||||||||||||
(In thousands, except per share amounts) | Shares | Amount | Income (Loss) | ||||||||||||||||||||||||||
31-Dec-13 | 46,356 | $ | 47,986 | $ | 840,521 | $ | (41,698 | ) | $ | 567,714 | $ | (2,128 | ) | $ | 1,412,395 | ||||||||||||||
Common stock issuances | 139 | 139 | 2,942 | 3,081 | |||||||||||||||||||||||||
Net income (loss) | 70,783 | (86 | ) | 70,697 | |||||||||||||||||||||||||
Other comprehensive income (loss): | |||||||||||||||||||||||||||||
Net actuarial gain (loss) arising during period, less amortization of unamortized benefit plan cost, net of tax | 512 | 512 | |||||||||||||||||||||||||||
Amounts reclassified to net income, net of tax (FSIRS) | 518 | 518 | |||||||||||||||||||||||||||
Dividends declared | |||||||||||||||||||||||||||||
Common: $0.365 per share | (17,193 | ) | (17,193 | ) | |||||||||||||||||||||||||
31-Mar-14 | 46,495 | $ | 48,125 | $ | 843,463 | $ | (40,668 | ) | $ | 621,304 | $ | (2,214 | ) | $ | 1,470,010 | ||||||||||||||
The following information provides insight into amounts impacting Other Comprehensive Income (Loss), both before and after-tax, within the Condensed Consolidated Statements of Comprehensive Income, which also impact Accumulated Other Comprehensive Income in the Company’s Condensed Consolidated Balance Sheets and the associated column in the equity table above. See Note 4 – Derivatives and Fair Value Measurements for additional information on the FSIRS. | |||||||||||||||||||||||||||||
Related Tax Effects Allocated to Each Component of Other Comprehensive Income (Loss) | |||||||||||||||||||||||||||||
(Thousands of dollars) | |||||||||||||||||||||||||||||
Three Months Ended | Three Months Ended | ||||||||||||||||||||||||||||
March 31, 2014 | March 31, 2013 | ||||||||||||||||||||||||||||
Before- | Tax | Net-of- | Before- | Tax | Net-of- | ||||||||||||||||||||||||
Tax | (Expense) | Tax | Tax | (Expense) | Tax | ||||||||||||||||||||||||
Amount | or Benefit (1) | Amount | Amount | or Benefit (1) | Amount | ||||||||||||||||||||||||
Defined benefit pension plans: | |||||||||||||||||||||||||||||
Amortization of net actuarial (gain)/loss | $ | 5,914 | $ | (2,247 | ) | $ | 3,667 | $ | 8,545 | $ | (3,247 | ) | $ | 5,298 | |||||||||||||||
Amortization of prior service cost | 89 | (34 | ) | 55 | 89 | (34 | ) | 55 | |||||||||||||||||||||
Regulatory adjustment | (5,178 | ) | 1,968 | (3,210 | ) | (7,584 | ) | 2,882 | (4,702 | ) | |||||||||||||||||||
Pension plans other comprehensive income (loss) | 825 | (313 | ) | 512 | 1,050 | (399 | ) | 651 | |||||||||||||||||||||
FSIRS (designated hedging activities): | |||||||||||||||||||||||||||||
Amounts reclassified into net income | 836 | (318 | ) | 518 | 836 | (318 | ) | 518 | |||||||||||||||||||||
FSIRS other comprehensive income | 836 | (318 | ) | 518 | 836 | (318 | ) | 518 | |||||||||||||||||||||
Total other comprehensive income (loss) | $ | 1,661 | $ | (631 | ) | $ | 1,030 | $ | 1,886 | $ | (717 | ) | $ | 1,169 | |||||||||||||||
Twelve Months Ended | Twelve Months Ended | ||||||||||||||||||||||||||||
March 31, 2014 | March 31, 2013 | ||||||||||||||||||||||||||||
Before- | Tax | Net-of- | Before- | Tax | Net-of- | ||||||||||||||||||||||||
Tax | (Expense) | Tax | Tax | (Expense) | Tax | ||||||||||||||||||||||||
Amount | or Benefit (1) | Amount | Amount | or Benefit (1) | Amount | ||||||||||||||||||||||||
Defined benefit pension plans: | |||||||||||||||||||||||||||||
Net actuarial gain/(loss) | $ | 100,345 | $ | (38,131 | ) | $ | 62,214 | $ | (74,853 | ) | $ | 28,444 | $ | (46,409 | ) | ||||||||||||||
Amortization of prior service cost | 355 | (135 | ) | 220 | 89 | (34 | ) | 55 | |||||||||||||||||||||
Amortization of transition obligation | — | — | — | 650 | (246 | ) | 404 | ||||||||||||||||||||||
Amortization of net actuarial (gain)/loss | 31,546 | (11,987 | ) | 19,559 | 27,742 | (10,542 | ) | 17,200 | |||||||||||||||||||||
Prior service cost | — | — | — | (2,423 | ) | 921 | (1,502 | ) | |||||||||||||||||||||
Regulatory adjustment | (121,224 | ) | 46,065 | (75,159 | ) | 41,036 | (15,594 | ) | 25,442 | ||||||||||||||||||||
Pension plans other comprehensive income (loss) | 11,022 | (4,188 | ) | 6,834 | (7,759 | ) | 2,949 | (4,810 | ) | ||||||||||||||||||||
FSIRS (designated hedging activities): | |||||||||||||||||||||||||||||
Amounts reclassified into net income | 3,345 | (1,271 | ) | 2,074 | 3,345 | (1,271 | ) | 2,074 | |||||||||||||||||||||
FSIRS other comprehensive income (loss) | 3,345 | (1,271 | ) | 2,074 | 3,345 | (1,271 | ) | 2,074 | |||||||||||||||||||||
Total other comprehensive income (loss) | $ | 14,367 | $ | (5,459 | ) | $ | 8,908 | $ | (4,414 | ) | $ | 1,678 | $ | (2,736 | ) | ||||||||||||||
Tax amounts are calculated using a 38% rate. | |||||||||||||||||||||||||||||
Approximately $2.1 million of realized losses (net of tax) related to the FSIRS, reported in Accumulated other comprehensive income (“AOCI”) at March 31, 2014, will be reclassified into interest expense within the next 12 months, as the related interest payments on long-term debt occur. | |||||||||||||||||||||||||||||
The following represents a rollforward of AOCI, presented on the Company’s Condensed Consolidated Balance Sheets: | |||||||||||||||||||||||||||||
AOCI—Rollforward | |||||||||||||||||||||||||||||
(Thousands of dollars) | |||||||||||||||||||||||||||||
Defined Benefit Plans | FSIRS | ||||||||||||||||||||||||||||
Before- | Tax | After- | Before- | Tax | After- | AOCI | |||||||||||||||||||||||
Tax | (Expense) | Tax | Tax | (Expense) | Tax | ||||||||||||||||||||||||
Benefit | Benefit | ||||||||||||||||||||||||||||
Beginning Balance AOCI December 31, 2013 | $ | (41,223 | ) | $ | 15,665 | $ | (25,558 | ) | $ | (26,033 | ) | $ | 9,893 | $ | (16,140 | ) | $ | (41,698 | ) | ||||||||||
Other comprehensive income before reclassifications | — | — | — | — | — | — | — | ||||||||||||||||||||||
FSIRS amounts reclassified from AOCI (1) | — | — | — | 836 | (318 | ) | 518 | 518 | |||||||||||||||||||||
Amortization of prior service cost (2) | 89 | (34 | ) | 55 | — | — | — | 55 | |||||||||||||||||||||
Amortization of net actuarial loss (2) | 5,914 | (2,247 | ) | 3,667 | — | — | — | 3,667 | |||||||||||||||||||||
Regulatory adjustment (3) | (5,178 | ) | 1,968 | (3,210 | ) | — | — | — | (3,210 | ) | |||||||||||||||||||
Net current period other comprehensive income (loss) | 825 | (313 | ) | 512 | 836 | (318 | ) | 518 | 1,030 | ||||||||||||||||||||
Ending Balance AOCI March 31, 2014 | $ | (40,398 | ) | $ | 15,352 | $ | (25,046 | ) | $ | (25,197 | ) | $ | 9,575 | $ | (15,622 | ) | $ | (40,668 | ) | ||||||||||
-1 | The FSIRS reclassification amounts are included in the Net interest deductions line item on the Condensed Consolidated Statements of Income. | ||||||||||||||||||||||||||||
-2 | These AOCI components are included in the computation of net periodic benefit cost (see Note 2 – Components of Net Periodic Benefit Cost for additional details). | ||||||||||||||||||||||||||||
-3 | The regulatory adjustment represents the portion of the activity above that is expected to be recovered through rates in the future (the related regulatory asset is included in the Deferred charges and other assets line item on the Condensed Consolidated Balance Sheets). | ||||||||||||||||||||||||||||
The following table represents amounts (before income tax impacts) included in AOCI (in the table above), that have not yet been recognized in net periodic benefit cost: | |||||||||||||||||||||||||||||
Amounts Recognized in AOCI (Before Tax) | |||||||||||||||||||||||||||||
(Thousands of dollars) | |||||||||||||||||||||||||||||
March 31, 2014 | December 31, 2013 | ||||||||||||||||||||||||||||
Net actuarial (loss) gain | $ | (283,227 | ) | $ | (289,141 | ) | |||||||||||||||||||||||
Prior service cost | (1,978 | ) | (2,067 | ) | |||||||||||||||||||||||||
Less: amount recognized in regulatory assets | 244,807 | 249,985 | |||||||||||||||||||||||||||
Recognized in AOCI | $ | (40,398 | ) | $ | (41,223 | ) | |||||||||||||||||||||||
Nature_of_Operations_and_Basis1
Nature of Operations and Basis of Presentation (Policies) | 3 Months Ended | ||||||||||||||||
Mar. 31, 2014 | |||||||||||||||||
Accounting Policies [Abstract] | ' | ||||||||||||||||
Nature of Operations | ' | ||||||||||||||||
Nature of Operations. Southwest Gas Corporation and its subsidiaries (the “Company”) consist of two segments: natural gas operations (“Southwest” or the “natural gas operations” segment) and construction services. Southwest is engaged in the business of purchasing, distributing, and transporting natural gas for customers in portions of Arizona, Nevada, and California. Public utility rates, practices, facilities, and service territories of Southwest are subject to regulatory oversight. The timing and amount of rate relief can materially impact results of operations. Natural gas sales are seasonal, peaking during the winter months; therefore, results of operations for interim periods are not necessarily indicative of results for a full year. Natural gas purchases and the timing of related recoveries can materially impact liquidity. NPL Construction Co. (“NPL” or the “construction services” segment), a wholly owned subsidiary, is a full-service underground piping contractor that primarily provides utility companies with trenching and installation, replacement, and maintenance services for energy distribution systems. Typically, NPL revenues are lowest during the first quarter of the year due to unfavorable winter weather conditions. Operating revenues typically improve as more favorable weather conditions occur during the summer and fall months. | |||||||||||||||||
Basis of Presentation | ' | ||||||||||||||||
Basis of Presentation. The condensed consolidated financial statements included herein have been prepared by the Company, without audit, pursuant to the rules and regulations of the Securities and Exchange Commission (the “SEC”). Certain information and footnote disclosures normally included in financial statements prepared in accordance with generally accepted accounting principles (“GAAP”) have been condensed or omitted pursuant to such rules and regulations. The preparation of the condensed consolidated financial statements requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements, and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates. In the opinion of management, all adjustments, consisting of normal recurring items and estimates necessary for a fair presentation of results for the interim periods, have been made. It is suggested that these condensed consolidated financial statements be read in conjunction with the consolidated financial statements and the notes thereto included in the 2013 Annual Report to Shareholders, which is incorporated by reference into the 2013 Form 10-K. | |||||||||||||||||
Prepaids and other current assets | ' | ||||||||||||||||
Prepaids and other current assets. Prepaids and other current assets includes gas pipe inventory and operating supplies of $21 million at both March 31, 2014 and December 31, 2013. | |||||||||||||||||
Cash and Cash Equivalents | ' | ||||||||||||||||
Cash and Cash Equivalents. For purposes of reporting consolidated cash flows, cash and cash equivalents include cash on hand and financial instruments with a purchase-date maturity of three months or less. Cash and cash equivalents fall within Level 1 (quoted prices for identical financial instruments) of the three-level fair value hierarchy that ranks the inputs used to measure fair value by their reliability. Upon contract expiration, customer advances of approximately $1.6 million and $2.8 million, during the first quarters of 2014 and 2013, respectively, were applied as contributions toward utility construction activity and represent non-cash investing activity. | |||||||||||||||||
Intercompany Transactions | ' | ||||||||||||||||
Intercompany Transactions. NPL recognizes revenues generated from contracts with Southwest (see Note 3 - Segment Information below). Accounts receivable for these services are presented in the table below (thousands of dollars): | |||||||||||||||||
March 31, 2014 | December 31, 2013 | ||||||||||||||||
Accounts receivable for NPL services | $ | 7,245 | $ | 10,787 | |||||||||||||
The accounts receivable balance, revenues, and associated profits are included in the condensed consolidated financial statements of the Company and were not eliminated during consolidation in accordance with accounting treatment for rate-regulated entities. | |||||||||||||||||
Other Property and Investments | ' | ||||||||||||||||
Other Property and Investments. Other property and investments includes (millions of dollars): | |||||||||||||||||
March 31, 2014 | December 31, 2013 | ||||||||||||||||
NPL property and equipment | $ | 325 | $ | 320 | |||||||||||||
NPL accumulated provision for depreciation and amortization | (168 | ) | (163 | ) | |||||||||||||
Net cash surrender value of COLI policies | 94 | 93 | |||||||||||||||
Other property | 11 | 11 | |||||||||||||||
Total | $ | 262 | $ | 261 | |||||||||||||
Other Income (Deductions) | ' | ||||||||||||||||
Other Income (Deductions). The following table provides the composition of significant items included in Other income (deductions) in the condensed consolidated statements of income (thousands of dollars): | |||||||||||||||||
Three Months Ended | Twelve Months Ended | ||||||||||||||||
March 31 | March 31 | ||||||||||||||||
2014 | 2013 | 2014 | 2013 | ||||||||||||||
Change in COLI policies | $ | 900 | $ | 3,800 | $ | 9,500 | $ | 5,200 | |||||||||
Interest income | 497 | 120 | 838 | 818 | |||||||||||||
Pipe replacement costs | — | (85 | ) | (47 | ) | (2,756 | ) | ||||||||||
Miscellaneous income and (expense) | 215 | 234 | (448 | ) | (210 | ) | |||||||||||
Total other income (deductions) | $ | 1,612 | $ | 4,069 | $ | 9,843 | $ | 3,052 | |||||||||
Included in the table above is the change in cash surrender values of company-owned life insurance (“COLI”) policies (including net death benefits recognized). These life insurance policies on members of management and other key employees are used by Southwest to indemnify itself against the loss of talent, expertise, and knowledge, as well as to provide indirect funding for certain nonqualified benefit plans. Current tax regulations provide for tax-free treatment of life insurance (death benefit) proceeds. Therefore, changes in the cash surrender value components of COLI policies, as they progress towards the ultimate death benefits, are also recorded without tax consequences. Pipe replacement costs include amounts associated with certain Arizona non-recoverable pipe replacement work. The replacement program work subject to non-recoverability was substantially completed in 2012. | |||||||||||||||||
Reclassifications | ' | ||||||||||||||||
Reclassifications. A reclassification was made to the prior year’s financial information between two categories on the Condensed Consolidated Statements of Comprehensive Income to present it on a basis comparable with the current year’s presentation, with no impact on comprehensive income overall. |
Nature_of_Operations_and_Basis2
Nature of Operations and Basis of Presentation (Tables) | 3 Months Ended | ||||||||||||||||
Mar. 31, 2014 | |||||||||||||||||
Accounting Policies [Abstract] | ' | ||||||||||||||||
Intercompany Transactions | ' | ||||||||||||||||
Accounts receivable for these services are presented in the table below (thousands of dollars): | |||||||||||||||||
March 31, 2014 | December 31, 2013 | ||||||||||||||||
Accounts receivable for NPL services | $ | 7,245 | $ | 10,787 | |||||||||||||
Schedule of Other Property and Investments | ' | ||||||||||||||||
Other property and investments includes (millions of dollars): | |||||||||||||||||
March 31, 2014 | December 31, 2013 | ||||||||||||||||
NPL property and equipment | $ | 325 | $ | 320 | |||||||||||||
NPL accumulated provision for depreciation and amortization | (168 | ) | (163 | ) | |||||||||||||
Net cash surrender value of COLI policies | 94 | 93 | |||||||||||||||
Other property | 11 | 11 | |||||||||||||||
Total | $ | 262 | $ | 261 | |||||||||||||
Other Income (Deductions) | ' | ||||||||||||||||
The following table provides the composition of significant items included in Other income (deductions) in the condensed consolidated statements of income (thousands of dollars): | |||||||||||||||||
Three Months Ended | Twelve Months Ended | ||||||||||||||||
March 31 | March 31 | ||||||||||||||||
2014 | 2013 | 2014 | 2013 | ||||||||||||||
Change in COLI policies | $ | 900 | $ | 3,800 | $ | 9,500 | $ | 5,200 | |||||||||
Interest income | 497 | 120 | 838 | 818 | |||||||||||||
Pipe replacement costs | — | (85 | ) | (47 | ) | (2,756 | ) | ||||||||||
Miscellaneous income and (expense) | 215 | 234 | (448 | ) | (210 | ) | |||||||||||
Total other income (deductions) | $ | 1,612 | $ | 4,069 | $ | 9,843 | $ | 3,052 | |||||||||
Components_of_Net_Periodic_Ben1
Components of Net Periodic Benefit Cost (Tables) | 3 Months Ended | ||||||||||||||||
Mar. 31, 2014 | |||||||||||||||||
Text Block [Abstract] | ' | ||||||||||||||||
Schedule of Components of Net Periodic Benefit Costs | ' | ||||||||||||||||
Net periodic benefit costs included in the table below are components of an overhead loading process associated with the cost of labor. The overhead process ultimately results in allocation of net periodic benefit costs to the same accounts to which productive labor is charged. As a result, net periodic benefit costs become components of various accounts, primarily operations and maintenance expense, net utility plant, and deferred charges and other assets. | |||||||||||||||||
Qualified Retirement Plan | |||||||||||||||||
Period Ended March 31, | |||||||||||||||||
Three Months | Twelve Months | ||||||||||||||||
(Thousands of dollars) | 2014 | 2013 | 2014 | 2013 | |||||||||||||
Service cost | $ | 5,340 | $ | 5,764 | $ | 22,632 | $ | 21,004 | |||||||||
Interest cost | 10,861 | 9,401 | 39,067 | 38,100 | |||||||||||||
Expected return on plan assets | (13,336 | ) | (12,460 | ) | (50,716 | ) | (46,795 | ) | |||||||||
Amortization of net actuarial loss | 5,718 | 8,066 | 29,913 | 25,978 | |||||||||||||
Net periodic benefit cost | $ | 8,583 | $ | 10,771 | $ | 40,896 | $ | 38,287 | |||||||||
SERP | |||||||||||||||||
Period Ended March 31, | |||||||||||||||||
Three Months | Twelve Months | ||||||||||||||||
(Thousands of dollars) | 2014 | 2013 | 2014 | 2013 | |||||||||||||
Service cost | $ | 73 | $ | 94 | $ | 352 | $ | 299 | |||||||||
Interest cost | 436 | 383 | 1,588 | 1,605 | |||||||||||||
Amortization of net actuarial loss | 196 | 243 | 924 | 755 | |||||||||||||
Net periodic benefit cost | $ | 705 | $ | 720 | $ | 2,864 | $ | 2,659 | |||||||||
PBOP | |||||||||||||||||
Period Ended March 31, | |||||||||||||||||
Three Months | Twelve Months | ||||||||||||||||
(Thousands of dollars) | 2014 | 2013 | 2014 | 2013 | |||||||||||||
Service cost | $ | 276 | $ | 305 | $ | 1,191 | $ | 1,037 | |||||||||
Interest cost | 707 | 620 | 2,569 | 2,531 | |||||||||||||
Expected return on plan assets | (816 | ) | (706 | ) | (2,934 | ) | (2,509 | ) | |||||||||
Amortization of prior service cost | 89 | 89 | 355 | 89 | |||||||||||||
Amortization of transition obligation | — | — | — | 650 | |||||||||||||
Amortization of net actuarial loss | — | 236 | 709 | 1,009 | |||||||||||||
Net periodic benefit cost | $ | 256 | $ | 544 | $ | 1,890 | $ | 2,807 | |||||||||
Segment_Information_Tables
Segment Information (Tables) | 3 Months Ended | ||||||||||||
Mar. 31, 2014 | |||||||||||||
Segment Reporting [Abstract] | ' | ||||||||||||
Schedule of Segment Reporting Information | ' | ||||||||||||
The following tables present revenues from external customers, intersegment revenues, and segment net income (thousands of dollars): | |||||||||||||
Natural Gas | Construction | Total | |||||||||||
Operations | Services | ||||||||||||
Three months ended March 31, 2014 | |||||||||||||
Revenues from external customers | $ | 486,493 | $ | 98,153 | $ | 584,646 | |||||||
Intersegment revenues | — | 23,750 | 23,750 | ||||||||||
Total | $ | 486,493 | $ | 121,903 | $ | 608,396 | |||||||
Segment net income (loss) | $ | 72,599 | $ | (1,816 | ) | $ | 70,783 | ||||||
Three months ended March 31, 2013 | |||||||||||||
Revenues from external customers | $ | 493,600 | $ | 104,866 | $ | 598,466 | |||||||
Intersegment revenues | — | 15,039 | 15,039 | ||||||||||
Total | $ | 493,600 | $ | 119,905 | $ | 613,505 | |||||||
Segment net income | $ | 79,292 | $ | 1,481 | $ | 80,773 | |||||||
Natural Gas | Construction | Total | |||||||||||
Operations | Services | ||||||||||||
Twelve months ended March 31, 2014 | |||||||||||||
Revenues from external customers | $ | 1,293,047 | $ | 555,762 | $ | 1,848,809 | |||||||
Intersegment revenues | — | 96,864 | 96,864 | ||||||||||
Total | $ | 1,293,047 | $ | 652,626 | $ | 1,945,673 | |||||||
Segment net income | $ | 117,476 | $ | 17,854 | $ | 135,330 | |||||||
Twelve months ended March 31, 2013 | |||||||||||||
Revenues from external customers | $ | 1,284,615 | $ | 516,655 | $ | 1,801,270 | |||||||
Intersegment revenues | — | 82,368 | 82,368 | ||||||||||
Total | $ | 1,284,615 | $ | 599,023 | $ | 1,883,638 | |||||||
Segment net income | $ | 116,545 | $ | 18,640 | $ | 135,185 | |||||||
Derivatives_and_Fair_Value_Mea1
Derivatives and Fair Value Measurements (Tables) | 3 Months Ended | ||||||||||||||||||
Mar. 31, 2014 | |||||||||||||||||||
Derivative Instruments And Hedging Activities Disclosure [Abstract] | ' | ||||||||||||||||||
Notional Amounts under Swaps Contracts | ' | ||||||||||||||||||
The differential is calculated based on the notional amounts under the contracts, which are detailed in the table below (thousands of dekatherms): | |||||||||||||||||||
March 31, 2014 | December 31, 2013 | ||||||||||||||||||
Contract notional amounts | 7,664 | 13,571 | |||||||||||||||||
Amount of Gain or Losses Recognized in Income on Derivatives | ' | ||||||||||||||||||
The following table sets forth the gains and (losses) recognized on the Company’s Swaps (derivatives) for the three-and twelve-month periods ended March 31, 2014 and 2013 and their location in the Condensed Consolidated Statements of Income (thousands of dollars): | |||||||||||||||||||
Gains (losses) recognized in income for derivatives not designated as hedging instruments: | |||||||||||||||||||
(Thousands of dollars) | |||||||||||||||||||
Location of Gain or (Loss) | Three Months Ended | Twelve Months Ended | |||||||||||||||||
Recognized in Income on Derivative | March 31 | March 31 | |||||||||||||||||
Instrument | 2014 | 2013 | 2014 | 2013 | |||||||||||||||
Swaps | Net cost of gas sold | $ | 5,990 | $ | 5,076 | $ | 1,890 | $ | 7,158 | ||||||||||
Swaps | Net cost of gas sold | (5,990 | )* | (5,076 | )* | (1,890 | )* | (7,158 | )* | ||||||||||
Total | $ | — | $ | — | $ | — | $ | — | |||||||||||
* | Represents the impact of regulatory deferral accounting treatment under U.S. GAAP for rate-regulated entities. | ||||||||||||||||||
Fair Values of Swaps in Condensed Consolidated Balance Sheets | ' | ||||||||||||||||||
The following table sets forth the fair values of the Company’s Swaps and their location in the Condensed Consolidated Balance Sheets (thousands of dollars): | |||||||||||||||||||
Fair values of derivatives not designated as hedging instruments: | |||||||||||||||||||
March 31, 2014 | Balance Sheet Location | Asset | Liability | Net Total | |||||||||||||||
Instrument | Derivatives | Derivatives | |||||||||||||||||
Swaps | Deferred charges and other assets | $ | 352 | $ | (16 | ) | $ | 336 | |||||||||||
Swaps | Prepaids and other current assets | 2,171 | — | 2,171 | |||||||||||||||
Total | $ | 2,523 | $ | (16 | ) | $ | 2,507 | ||||||||||||
31-Dec-13 | Balance Sheet Location | Asset | Liability | Net Total | |||||||||||||||
Instrument | Derivatives | Derivatives | |||||||||||||||||
Swaps | Deferred charges and other assets | $ | 257 | $ | (77 | ) | $ | 180 | |||||||||||
Swaps | Prepaids and other current assets | 1,054 | (253 | ) | 801 | ||||||||||||||
Swaps | Other current liabilities | 126 | (282 | ) | (156 | ) | |||||||||||||
Swaps | Other deferred credits | 7 | (11 | ) | (4 | ) | |||||||||||||
Total | $ | 1,444 | $ | (623 | ) | $ | 821 | ||||||||||||
Paid to and Received from Counterparties for Settlements of Matured Swaps | ' | ||||||||||||||||||
The following table shows the amounts Southwest paid to and received from counterparties for settlements of matured Swaps. | |||||||||||||||||||
(Thousands of dollars) | Three Months Ended | Twelve Months Ended | |||||||||||||||||
March 31, 2014 | March 31, 2014 | ||||||||||||||||||
Paid to counterparties | $ | 15 | $ | 2,294 | |||||||||||||||
Received from counterparties | $ | 4,319 | $ | 4,869 | |||||||||||||||
Regulatory Assets/Liabilities Offsetting Derivatives at Fair Value in Condensed Consolidated Balance Sheets | ' | ||||||||||||||||||
The following table details the regulatory assets/(liabilities) offsetting the derivatives at fair value in the Condensed Consolidated Balance Sheets (thousands of dollars). | |||||||||||||||||||
March 31, 2014 | Balance Sheet Location | Net Total | |||||||||||||||||
Instrument | |||||||||||||||||||
Swaps | Other deferred credits | $ | (336 | ) | |||||||||||||||
Swaps | Other current liabilities | (2,171 | ) | ||||||||||||||||
31-Dec-13 | Balance Sheet Location | Net Total | |||||||||||||||||
Instrument | |||||||||||||||||||
Swaps | Other deferred credits | $ | (180 | ) | |||||||||||||||
Swaps | Other current liabilities | (801 | ) | ||||||||||||||||
Swaps | Prepaids and other current assets | 156 | |||||||||||||||||
Swaps | Deferred charges and other assets | 4 | |||||||||||||||||
Significant Other Observable Inputs | ' | ||||||||||||||||||
The following table sets forth by level within the three-level fair value hierarchy that ranks the inputs used to measure fair value by their reliability, the Company’s financial assets and liabilities recorded at fair value: | |||||||||||||||||||
Level 2 – Significant other observable inputs | |||||||||||||||||||
(Thousands of dollars) | March 31, 2014 | December 31, 2013 | |||||||||||||||||
Assets at fair value: | |||||||||||||||||||
Prepaids and other current assets—Swaps | $ | 2,171 | $ | 801 | |||||||||||||||
Deferred charges and other assets—Swaps | 336 | 180 | |||||||||||||||||
Liabilities at fair value: | |||||||||||||||||||
Other current liabilities—Swaps | — | (156 | ) | ||||||||||||||||
Other deferred credits—Swaps | — | (4 | ) | ||||||||||||||||
Net Assets (Liabilities) | $ | 2,507 | $ | 821 | |||||||||||||||
LongTerm_Debt_Tables
Long-Term Debt (Tables) | 3 Months Ended | ||||||||||||||||
Mar. 31, 2014 | |||||||||||||||||
Debt Disclosure [Abstract] | ' | ||||||||||||||||
Schedule of Carrying Amounts and Estimated Fair Values of Long-Term Debt | ' | ||||||||||||||||
The external credit rating, coupon rate, and maturity of each security are considered in the valuation, as applicable. | |||||||||||||||||
March 31, 2014 | December 31, 2013 | ||||||||||||||||
(Thousands of dollars) | Carrying | Market | Carrying | Market | |||||||||||||
Amount | Value | Amount | Value | ||||||||||||||
Debentures: | |||||||||||||||||
Notes, 4.45%, due 2020 | $ | 125,000 | $ | 134,433 | $ | 125,000 | $ | 130,953 | |||||||||
Notes, 6.1%, due 2041 | 125,000 | 148,894 | 125,000 | 141,873 | |||||||||||||
Notes, 3.875%, due 2022 | 250,000 | 255,923 | 250,000 | 252,485 | |||||||||||||
Notes, 4.875%, due 2043 | 250,000 | 268,873 | 250,000 | 257,280 | |||||||||||||
8% Series, due 2026 | 75,000 | 101,735 | 75,000 | 96,263 | |||||||||||||
Medium-term notes, 7.59% series, due 2017 | 25,000 | 28,691 | 25,000 | 28,741 | |||||||||||||
Medium-term notes, 7.78% series, due 2022 | 25,000 | 31,585 | 25,000 | 30,586 | |||||||||||||
Medium-term notes, 7.92% series, due 2027 | 25,000 | 33,402 | 25,000 | 31,497 | |||||||||||||
Medium-term notes, 6.76% series, due 2027 | 7,500 | 9,021 | 7,500 | 8,468 | |||||||||||||
Unamortized discount | (5,478 | ) | (5,560 | ) | |||||||||||||
902,022 | 901,940 | ||||||||||||||||
Revolving credit facility and commercial paper | — | — | 10,000 | 10,000 | |||||||||||||
Industrial development revenue bonds: | |||||||||||||||||
Variable-rate bonds: | |||||||||||||||||
Tax-exempt Series A, due 2028 | 50,000 | 50,000 | 50,000 | 50,000 | |||||||||||||
2003 Series A, due 2038 | 50,000 | 50,000 | 50,000 | 50,000 | |||||||||||||
2008 Series A, due 2038 | 50,000 | 50,000 | 50,000 | 50,000 | |||||||||||||
2009 Series A, due 2039 | 50,000 | 50,000 | 50,000 | 50,000 | |||||||||||||
Fixed-rate bonds: | |||||||||||||||||
5.25% 2003 Series D, due 2038 | 20,000 | 20,289 | 20,000 | 20,150 | |||||||||||||
5.25% 2004 Series A, due 2034 | 65,000 | 65,051 | 65,000 | 64,522 | |||||||||||||
5.00% 2004 Series B, due 2033 | 31,200 | 31,229 | 31,200 | 30,284 | |||||||||||||
4.85% 2005 Series A, due 2035 | 100,000 | 99,709 | 100,000 | 95,192 | |||||||||||||
4.75% 2006 Series A, due 2036 | 24,855 | 24,539 | 24,855 | 22,974 | |||||||||||||
Unamortized discount | (2,743 | ) | (2,776 | ) | |||||||||||||
438,312 | 438,279 | ||||||||||||||||
NPL credit facility | — | — | — | — | |||||||||||||
NPL other debt obligations | 39,456 | 39,465 | 42,213 | 42,119 | |||||||||||||
1,379,790 | 1,392,432 | ||||||||||||||||
Less: current maturities | (11,158 | ) | (11,105 | ) | |||||||||||||
Long-term debt, less current maturities | $ | 1,368,632 | $ | 1,381,327 | |||||||||||||
Equity_Other_Comprehensive_Inc1
Equity, Other Comprehensive Income, and Accumulated Other Comprehensive Income (Tables) | 3 Months Ended | ||||||||||||||||||||||||||||
Mar. 31, 2014 | |||||||||||||||||||||||||||||
Text Block [Abstract] | ' | ||||||||||||||||||||||||||||
Detailed Activities of Equity | ' | ||||||||||||||||||||||||||||
The table below provides details of activity in equity during the three months ended March 31, 2014. | |||||||||||||||||||||||||||||
Southwest Gas Corporation Equity | |||||||||||||||||||||||||||||
Common Stock | Additional | Accumulated | Retained | Non- | Total | ||||||||||||||||||||||||
Paid-in | Other | Earnings | controlling | ||||||||||||||||||||||||||
Capital | Comprehensive | Interest | |||||||||||||||||||||||||||
(In thousands, except per share amounts) | Shares | Amount | Income (Loss) | ||||||||||||||||||||||||||
31-Dec-13 | 46,356 | $ | 47,986 | $ | 840,521 | $ | (41,698 | ) | $ | 567,714 | $ | (2,128 | ) | $ | 1,412,395 | ||||||||||||||
Common stock issuances | 139 | 139 | 2,942 | 3,081 | |||||||||||||||||||||||||
Net income (loss) | 70,783 | (86 | ) | 70,697 | |||||||||||||||||||||||||
Other comprehensive income (loss): | |||||||||||||||||||||||||||||
Net actuarial gain (loss) arising during period, less amortization of unamortized benefit plan cost, net of tax | 512 | 512 | |||||||||||||||||||||||||||
Amounts reclassified to net income, net of tax (FSIRS) | 518 | 518 | |||||||||||||||||||||||||||
Dividends declared | |||||||||||||||||||||||||||||
Common: $0.365 per share | (17,193 | ) | (17,193 | ) | |||||||||||||||||||||||||
31-Mar-14 | 46,495 | $ | 48,125 | $ | 843,463 | $ | (40,668 | ) | $ | 621,304 | $ | (2,214 | ) | $ | 1,470,010 | ||||||||||||||
Related Tax Effects Allocated to Each Component of Other Comprehensive Income (Loss) | ' | ||||||||||||||||||||||||||||
Related Tax Effects Allocated to Each Component of Other Comprehensive Income (Loss) | |||||||||||||||||||||||||||||
(Thousands of dollars) | |||||||||||||||||||||||||||||
Three Months Ended | Three Months Ended | ||||||||||||||||||||||||||||
March 31, 2014 | March 31, 2013 | ||||||||||||||||||||||||||||
Before- | Tax | Net-of- | Before- | Tax | Net-of- | ||||||||||||||||||||||||
Tax | (Expense) | Tax | Tax | (Expense) | Tax | ||||||||||||||||||||||||
Amount | or Benefit (1) | Amount | Amount | or Benefit (1) | Amount | ||||||||||||||||||||||||
Defined benefit pension plans: | |||||||||||||||||||||||||||||
Amortization of net actuarial (gain)/loss | $ | 5,914 | $ | (2,247 | ) | $ | 3,667 | $ | 8,545 | $ | (3,247 | ) | $ | 5,298 | |||||||||||||||
Amortization of prior service cost | 89 | (34 | ) | 55 | 89 | (34 | ) | 55 | |||||||||||||||||||||
Regulatory adjustment | (5,178 | ) | 1,968 | (3,210 | ) | (7,584 | ) | 2,882 | (4,702 | ) | |||||||||||||||||||
Pension plans other comprehensive income (loss) | 825 | (313 | ) | 512 | 1,050 | (399 | ) | 651 | |||||||||||||||||||||
FSIRS (designated hedging activities): | |||||||||||||||||||||||||||||
Amounts reclassified into net income | 836 | (318 | ) | 518 | 836 | (318 | ) | 518 | |||||||||||||||||||||
FSIRS other comprehensive income | 836 | (318 | ) | 518 | 836 | (318 | ) | 518 | |||||||||||||||||||||
Total other comprehensive income (loss) | $ | 1,661 | $ | (631 | ) | $ | 1,030 | $ | 1,886 | $ | (717 | ) | $ | 1,169 | |||||||||||||||
Twelve Months Ended | Twelve Months Ended | ||||||||||||||||||||||||||||
March 31, 2014 | March 31, 2013 | ||||||||||||||||||||||||||||
Before- | Tax | Net-of- | Before- | Tax | Net-of- | ||||||||||||||||||||||||
Tax | (Expense) | Tax | Tax | (Expense) | Tax | ||||||||||||||||||||||||
Amount | or Benefit (1) | Amount | Amount | or Benefit (1) | Amount | ||||||||||||||||||||||||
Defined benefit pension plans: | |||||||||||||||||||||||||||||
Net actuarial gain/(loss) | $ | 100,345 | $ | (38,131 | ) | $ | 62,214 | $ | (74,853 | ) | $ | 28,444 | $ | (46,409 | ) | ||||||||||||||
Amortization of prior service cost | 355 | (135 | ) | 220 | 89 | (34 | ) | 55 | |||||||||||||||||||||
Amortization of transition obligation | — | — | — | 650 | (246 | ) | 404 | ||||||||||||||||||||||
Amortization of net actuarial (gain)/loss | 31,546 | (11,987 | ) | 19,559 | 27,742 | (10,542 | ) | 17,200 | |||||||||||||||||||||
Prior service cost | — | — | — | (2,423 | ) | 921 | (1,502 | ) | |||||||||||||||||||||
Regulatory adjustment | (121,224 | ) | 46,065 | (75,159 | ) | 41,036 | (15,594 | ) | 25,442 | ||||||||||||||||||||
Pension plans other comprehensive income (loss) | 11,022 | (4,188 | ) | 6,834 | (7,759 | ) | 2,949 | (4,810 | ) | ||||||||||||||||||||
FSIRS (designated hedging activities): | |||||||||||||||||||||||||||||
Amounts reclassified into net income | 3,345 | (1,271 | ) | 2,074 | 3,345 | (1,271 | ) | 2,074 | |||||||||||||||||||||
FSIRS other comprehensive income (loss) | 3,345 | (1,271 | ) | 2,074 | 3,345 | (1,271 | ) | 2,074 | |||||||||||||||||||||
Total other comprehensive income (loss) | $ | 14,367 | $ | (5,459 | ) | $ | 8,908 | $ | (4,414 | ) | $ | 1,678 | $ | (2,736 | ) | ||||||||||||||
Tax amounts are calculated using a 38% rate. | |||||||||||||||||||||||||||||
Rollforward of Accumulated Other Comprehensive Income | ' | ||||||||||||||||||||||||||||
The following represents a rollforward of AOCI, presented on the Company’s Condensed Consolidated Balance Sheets: | |||||||||||||||||||||||||||||
AOCI—Rollforward | |||||||||||||||||||||||||||||
(Thousands of dollars) | |||||||||||||||||||||||||||||
Defined Benefit Plans | FSIRS | ||||||||||||||||||||||||||||
Before- | Tax | After- | Before- | Tax | After- | AOCI | |||||||||||||||||||||||
Tax | (Expense) | Tax | Tax | (Expense) | Tax | ||||||||||||||||||||||||
Benefit | Benefit | ||||||||||||||||||||||||||||
Beginning Balance AOCI December 31, 2013 | $ | (41,223 | ) | $ | 15,665 | $ | (25,558 | ) | $ | (26,033 | ) | $ | 9,893 | $ | (16,140 | ) | $ | (41,698 | ) | ||||||||||
Other comprehensive income before reclassifications | — | — | — | — | — | — | — | ||||||||||||||||||||||
FSIRS amounts reclassified from AOCI (1) | — | — | — | 836 | (318 | ) | 518 | 518 | |||||||||||||||||||||
Amortization of prior service cost (2) | 89 | (34 | ) | 55 | — | — | — | 55 | |||||||||||||||||||||
Amortization of net actuarial loss (2) | 5,914 | (2,247 | ) | 3,667 | — | — | — | 3,667 | |||||||||||||||||||||
Regulatory adjustment (3) | (5,178 | ) | 1,968 | (3,210 | ) | — | — | — | (3,210 | ) | |||||||||||||||||||
Net current period other comprehensive income (loss) | 825 | (313 | ) | 512 | 836 | (318 | ) | 518 | 1,030 | ||||||||||||||||||||
Ending Balance AOCI March 31, 2014 | $ | (40,398 | ) | $ | 15,352 | $ | (25,046 | ) | $ | (25,197 | ) | $ | 9,575 | $ | (15,622 | ) | $ | (40,668 | ) | ||||||||||
-1 | The FSIRS reclassification amounts are included in the Net interest deductions line item on the Condensed Consolidated Statements of Income. | ||||||||||||||||||||||||||||
-2 | These AOCI components are included in the computation of net periodic benefit cost (see Note 2 – Components of Net Periodic Benefit Cost for additional details). | ||||||||||||||||||||||||||||
-3 | The regulatory adjustment represents the portion of the activity above that is expected to be recovered through rates in the future (the related regulatory asset is included in the Deferred charges and other assets line item on the Condensed Consolidated Balance Sheets). | ||||||||||||||||||||||||||||
Amount Recognized Before Income Tax in Accumulated Other Comprehensive Income | ' | ||||||||||||||||||||||||||||
The following table represents amounts (before income tax impacts) included in AOCI (in the table above), that have not yet been recognized in net periodic benefit cost: | |||||||||||||||||||||||||||||
Amounts Recognized in AOCI (Before Tax) | |||||||||||||||||||||||||||||
(Thousands of dollars) | |||||||||||||||||||||||||||||
March 31, 2014 | December 31, 2013 | ||||||||||||||||||||||||||||
Net actuarial (loss) gain | $ | (283,227 | ) | $ | (289,141 | ) | |||||||||||||||||||||||
Prior service cost | (1,978 | ) | (2,067 | ) | |||||||||||||||||||||||||
Less: amount recognized in regulatory assets | 244,807 | 249,985 | |||||||||||||||||||||||||||
Recognized in AOCI | $ | (40,398 | ) | $ | (41,223 | ) | |||||||||||||||||||||||
Nature_of_Operations_and_Basis3
Nature of Operations and Basis of Presentation - Additional Information (Detail) (USD $) | 3 Months Ended | |||
In Millions, unless otherwise specified | Mar. 31, 2014 | Mar. 31, 2013 | Mar. 31, 2014 | Dec. 31, 2013 |
Gas pipe inventory and operating supplies [Member] | Gas pipe inventory and operating supplies [Member] | |||
Significant Accounting Policies [Line Items] | ' | ' | ' | ' |
Gas pipe inventory and operating supplies | ' | ' | $21 | $21 |
Non-cash construction advances - non-cash investing item | $1.60 | $2.80 | ' | ' |
Nature_of_Operations_and_Basis4
Nature of Operations and Basis of Presentation - Intercompany Transactions (Detail) (NPL Construction Co. [Member], USD $) | Mar. 31, 2014 | Dec. 31, 2013 |
In Thousands, unless otherwise specified | ||
NPL Construction Co. [Member] | ' | ' |
Accounts receivable for NPL services | $7,245 | $10,787 |
Nature_of_Operations_and_Basis5
Nature of Operations and Basis of Presentation - Schedule of Other Property and Investments (Detail) (USD $) | Mar. 31, 2014 | Dec. 31, 2013 |
Investment [Line Items] | ' | ' |
Net cash surrender value of COLI policies | $94,000,000 | $93,000,000 |
Other property | 11,000,000 | 11,000,000 |
Total | 262,187,000 | 260,871,000 |
NPL Construction Co. [Member] | ' | ' |
Investment [Line Items] | ' | ' |
NPL property and equipment | 325,000,000 | 320,000,000 |
NPL accumulated provision for depreciation and amortization | ($168,000,000) | ($163,000,000) |
Nature_of_Operations_and_Basis6
Nature of Operations and Basis of Presentation - Other Income (Deductions) (Detail) (USD $) | 3 Months Ended | 12 Months Ended | ||
In Thousands, unless otherwise specified | Mar. 31, 2014 | Mar. 31, 2013 | Mar. 31, 2014 | Mar. 31, 2013 |
Other Income And Expenses [Abstract] | ' | ' | ' | ' |
Change in COLI policies | $900 | $3,800 | $9,500 | $5,200 |
Interest income | 497 | 120 | 838 | 818 |
Pipe replacement costs | ' | -85 | -47 | -2,756 |
Miscellaneous income and (expense) | 215 | 234 | -448 | -210 |
Total other income (deductions) | $1,612 | $4,069 | $9,843 | $3,052 |
Components_of_Net_Periodic_Ben2
Components of Net Periodic Benefit Cost - Schedule of Components of Net Periodic Benefit Costs (Detail) (USD $) | 3 Months Ended | 12 Months Ended | ||
In Thousands, unless otherwise specified | Mar. 31, 2014 | Mar. 31, 2013 | Mar. 31, 2014 | Mar. 31, 2013 |
Qualified Retirement Plan [Member] | ' | ' | ' | ' |
Defined Benefit Plan Disclosure [Line Items] | ' | ' | ' | ' |
Service cost | $5,340 | $5,764 | $22,632 | $21,004 |
Interest cost | 10,861 | 9,401 | 39,067 | 38,100 |
Expected return on plan assets | -13,336 | -12,460 | -50,716 | -46,795 |
Amortization of net actuarial loss | 5,718 | 8,066 | 29,913 | 25,978 |
Net periodic benefit cost | 8,583 | 10,771 | 40,896 | 38,287 |
SERP [Member] | ' | ' | ' | ' |
Defined Benefit Plan Disclosure [Line Items] | ' | ' | ' | ' |
Service cost | 73 | 94 | 352 | 299 |
Interest cost | 436 | 383 | 1,588 | 1,605 |
Amortization of net actuarial loss | 196 | 243 | 924 | 755 |
Net periodic benefit cost | 705 | 720 | 2,864 | 2,659 |
PBOP [Member] | ' | ' | ' | ' |
Defined Benefit Plan Disclosure [Line Items] | ' | ' | ' | ' |
Service cost | 276 | 305 | 1,191 | 1,037 |
Interest cost | 707 | 620 | 2,569 | 2,531 |
Expected return on plan assets | -816 | -706 | -2,934 | -2,509 |
Amortization of prior service cost | 89 | 89 | 355 | 89 |
Amortization of transition obligation | ' | ' | ' | 650 |
Amortization of net actuarial loss | ' | 236 | 709 | 1,009 |
Net periodic benefit cost | $256 | $544 | $1,890 | $2,807 |
Segment_Information_Schedule_o
Segment Information - Schedule of Segment Reporting Information (Detail) (USD $) | 3 Months Ended | 12 Months Ended | ||
In Thousands, unless otherwise specified | Mar. 31, 2014 | Mar. 31, 2013 | Mar. 31, 2014 | Mar. 31, 2013 |
Segment Reporting Information [Line Items] | ' | ' | ' | ' |
Total operating revenues | $608,396 | $613,505 | $1,945,673 | $1,883,638 |
Segment net income (loss) | 70,783 | 80,773 | 135,330 | 135,185 |
Revenues from external customers [Member] | ' | ' | ' | ' |
Segment Reporting Information [Line Items] | ' | ' | ' | ' |
Revenues | 584,646 | 598,466 | 1,848,809 | 1,801,270 |
Intersegment revenues [Member] | ' | ' | ' | ' |
Segment Reporting Information [Line Items] | ' | ' | ' | ' |
Revenues | 23,750 | 15,039 | 96,864 | 82,368 |
Natural Gas Operations [Member] | ' | ' | ' | ' |
Segment Reporting Information [Line Items] | ' | ' | ' | ' |
Total operating revenues | 486,493 | 493,600 | 1,293,047 | 1,284,615 |
Segment net income (loss) | 72,599 | 79,292 | 117,476 | 116,545 |
Natural Gas Operations [Member] | Revenues from external customers [Member] | ' | ' | ' | ' |
Segment Reporting Information [Line Items] | ' | ' | ' | ' |
Revenues | 486,493 | 493,600 | 1,293,047 | 1,284,615 |
Natural Gas Operations [Member] | Intersegment revenues [Member] | ' | ' | ' | ' |
Segment Reporting Information [Line Items] | ' | ' | ' | ' |
Revenues | ' | ' | ' | ' |
Construction Services [Member] | ' | ' | ' | ' |
Segment Reporting Information [Line Items] | ' | ' | ' | ' |
Total operating revenues | 121,903 | 119,905 | 652,626 | 599,023 |
Segment net income (loss) | -1,816 | 1,481 | 17,854 | 18,640 |
Construction Services [Member] | Revenues from external customers [Member] | ' | ' | ' | ' |
Segment Reporting Information [Line Items] | ' | ' | ' | ' |
Revenues | 98,153 | 104,866 | 555,762 | 516,655 |
Construction Services [Member] | Intersegment revenues [Member] | ' | ' | ' | ' |
Segment Reporting Information [Line Items] | ' | ' | ' | ' |
Revenues | $23,750 | $15,039 | $96,864 | $82,368 |
Derivatives_and_Fair_Value_Mea2
Derivatives and Fair Value Measurements - Additional Information (Detail) (USD $) | 3 Months Ended | 12 Months Ended | ||
Mar. 31, 2014 | Mar. 31, 2013 | Mar. 31, 2014 | Mar. 31, 2013 | |
Derivative [Line Items] | ' | ' | ' | ' |
Natural gas portfolios, maximum % rate | 35.00% | ' | ' | ' |
Gains (losses) recognized in income or other comprehensive income for derivative designated cash flow hedges | $518,000 | $518,000 | $2,074,000 | $2,074,000 |
Derivative instrument loss at settlement amortization period | '10 years | ' | ' | ' |
Cash flow hedging [Member] | ' | ' | ' | ' |
Derivative [Line Items] | ' | ' | ' | ' |
Gains (losses) recognized in income or other comprehensive income for derivative designated cash flow hedges | 0 | ' | ' | ' |
Settlement at maturity of the first FSIRS [Member] | ' | ' | ' | ' |
Derivative [Line Items] | ' | ' | ' | ' |
Agreement settlement paid | 11,700,000 | ' | ' | ' |
Settlement at maturity of the second FSIRS [Member] | ' | ' | ' | ' |
Derivative [Line Items] | ' | ' | ' | ' |
Agreement settlement paid | $21,800,000 | ' | ' | ' |
Minimum [Member] | ' | ' | ' | ' |
Derivative [Line Items] | ' | ' | ' | ' |
Maturities of natural gas swaps | 1-Apr-14 | ' | ' | ' |
Maximum [Member] | ' | ' | ' | ' |
Derivative [Line Items] | ' | ' | ' | ' |
Maturities of natural gas swaps | 1-Mar-16 | ' | ' | ' |
Derivatives_and_Fair_Value_Mea3
Derivatives and Fair Value Measurements - Notional Amounts under Swaps Contracts (Detail) | Mar. 31, 2014 | Dec. 31, 2013 |
MMBTU | MMBTU | |
Offsetting [Abstract] | ' | ' |
Contract notional amounts | 7,664,000 | 13,571,000 |
Derivatives_and_Fair_Value_Mea4
Derivatives and Fair Value Measurements - Amount of Gain or Losses Recognized in Income on Derivatives (Detail) (USD $) | 3 Months Ended | 12 Months Ended | ||
In Thousands, unless otherwise specified | Mar. 31, 2014 | Mar. 31, 2013 | Mar. 31, 2014 | Mar. 31, 2013 |
Derivative Instruments, Gain (Loss) [Line Items] | ' | ' | ' | ' |
Amount of gain or (loss) recognized in income on derivative | ' | ' | ' | ' |
Cash flow hedging [Member] | Net cost of gas sold [Member] | ' | ' | ' | ' |
Derivative Instruments, Gain (Loss) [Line Items] | ' | ' | ' | ' |
Amount of gain or (loss) recognized in income on derivative | 5,990 | 5,076 | 1,890 | 7,158 |
Regulatory deferral accounting treatment [Member] | Cash flow hedging [Member] | Net cost of gas sold [Member] | ' | ' | ' | ' |
Derivative Instruments, Gain (Loss) [Line Items] | ' | ' | ' | ' |
Amount of gain or (loss) recognized in income on derivative | ($5,990) | ($5,076) | ($1,890) | ($7,158) |
Derivatives_and_Fair_Value_Mea5
Derivatives and Fair Value Measurements - Fair Values of Swaps in Condensed Consolidated Balance Sheets (Detail) (USD $) | Mar. 31, 2014 | Dec. 31, 2013 |
In Thousands, unless otherwise specified | ||
Derivatives, Fair Value [Line Items] | ' | ' |
Asset derivatives not designated as hedging instruments | $2,523 | $1,444 |
Liability derivatives not designated as hedging instruments | -16 | -623 |
Net total not designated as hedging instruments | 2,507 | 821 |
Swaps [Member] | Deferred charges and other assets [Member] | ' | ' |
Derivatives, Fair Value [Line Items] | ' | ' |
Asset derivatives not designated as hedging instruments | 352 | 257 |
Liability derivatives not designated as hedging instruments | -16 | -77 |
Net total not designated as hedging instruments | 336 | 180 |
Swaps [Member] | Prepaids and other current assets [Member] | ' | ' |
Derivatives, Fair Value [Line Items] | ' | ' |
Asset derivatives not designated as hedging instruments | 2,171 | 1,054 |
Liability derivatives not designated as hedging instruments | ' | -253 |
Net total not designated as hedging instruments | 2,171 | 801 |
Swaps [Member] | Other current liabilities [Member] | ' | ' |
Derivatives, Fair Value [Line Items] | ' | ' |
Asset derivatives not designated as hedging instruments | ' | 126 |
Liability derivatives not designated as hedging instruments | ' | -282 |
Net total not designated as hedging instruments | ' | -156 |
Swaps [Member] | Other deferred credits [Member] | ' | ' |
Derivatives, Fair Value [Line Items] | ' | ' |
Asset derivatives not designated as hedging instruments | ' | 7 |
Liability derivatives not designated as hedging instruments | ' | -11 |
Net total not designated as hedging instruments | ' | ($4) |
Derivatives_and_Fair_Value_Mea6
Derivatives and Fair Value Measurements - Paid to and Received from Counterparties for Settlements of Matured Swaps (Detail) (USD $) | 3 Months Ended | 12 Months Ended |
In Thousands, unless otherwise specified | Mar. 31, 2014 | Mar. 31, 2014 |
Derivative Instruments And Hedging Activities Disclosure [Abstract] | ' | ' |
Paid to counterparties | $15 | $2,294 |
Received from counterparties | $4,319 | $4,869 |
Derivatives_and_Fair_Value_Mea7
Derivatives and Fair Value Measurements - Regulatory Assets/Liabilities Offsetting Derivatives at Fair Value in Condensed Consolidated Balance Sheets (Detail) (Swaps [Member], USD $) | Mar. 31, 2014 | Dec. 31, 2013 |
In Thousands, unless otherwise specified | ||
Other deferred credits [Member] | ' | ' |
Derivatives, Fair Value [Line Items] | ' | ' |
Net Total | ($336) | ($180) |
Other current liabilities [Member] | ' | ' |
Derivatives, Fair Value [Line Items] | ' | ' |
Net Total | -2,171 | -801 |
Prepaids and other current assets [Member] | ' | ' |
Derivatives, Fair Value [Line Items] | ' | ' |
Net Total | ' | 156 |
Deferred charges and other assets [Member] | ' | ' |
Derivatives, Fair Value [Line Items] | ' | ' |
Net Total | ' | $4 |
Derivatives_and_Fair_Value_Mea8
Derivatives and Fair Value Measurements - Significant Other Observable Inputs (Detail) (Level 2 - Significant other observable inputs [Member], USD $) | Mar. 31, 2014 | Dec. 31, 2013 |
In Thousands, unless otherwise specified | ||
Derivatives, Fair Value [Line Items] | ' | ' |
Net Assets (Liabilities) | $2,507 | $821 |
Swaps [Member] | Prepaids and other current assets [Member] | ' | ' |
Derivatives, Fair Value [Line Items] | ' | ' |
Derivative Assets | 2,171 | 801 |
Swaps [Member] | Deferred charges and other assets [Member] | ' | ' |
Derivatives, Fair Value [Line Items] | ' | ' |
Derivative Assets | 336 | 180 |
Swaps [Member] | Other current liabilities [Member] | ' | ' |
Derivatives, Fair Value [Line Items] | ' | ' |
Derivative Liabilities | ' | -156 |
Swaps [Member] | Other deferred credits [Member] | ' | ' |
Derivatives, Fair Value [Line Items] | ' | ' |
Derivative Liabilities | ' | ($4) |
LongTerm_Debt_Schedule_of_Carr
Long-Term Debt - Schedule of Carrying Amounts and Estimated Fair Values of Long-Term Debt (Detail) (USD $) | Mar. 31, 2014 | Dec. 31, 2013 |
In Thousands, unless otherwise specified | ||
Debt Instrument [Line Items] | ' | ' |
Less: current maturities | ($11,158) | ($11,105) |
Long-term debt, less current maturities | 1,368,632 | 1,381,327 |
Notes, 6.1%, due 2041 [Member] | ' | ' |
Debt Instrument [Line Items] | ' | ' |
Notes payable | 125,000 | ' |
Carrying Amount [Member] | ' | ' |
Debt Instrument [Line Items] | ' | ' |
NPL credit facility | ' | ' |
Unamortized discount | -2,743 | -2,776 |
Long-term debt, gross | 1,379,790 | 1,392,432 |
Less: current maturities | -11,158 | -11,105 |
Long-term debt, less current maturities | 1,368,632 | 1,381,327 |
Carrying Amount [Member] | Bonds [Member] | ' | ' |
Debt Instrument [Line Items] | ' | ' |
Unsecured debt | 438,312 | 438,279 |
Carrying Amount [Member] | NPL other debt obligations [Member] | ' | ' |
Debt Instrument [Line Items] | ' | ' |
NPL other debt obligations | 39,456 | 42,213 |
Carrying Amount [Member] | Debentures [Member] | ' | ' |
Debt Instrument [Line Items] | ' | ' |
Unamortized discount | -5,478 | -5,560 |
Carrying Amount [Member] | Debentures [Member] | Notes, 4.45%, due 2020 [Member] | ' | ' |
Debt Instrument [Line Items] | ' | ' |
Notes payable | 125,000 | 125,000 |
Carrying Amount [Member] | Debentures [Member] | Notes, 6.1%, due 2041 [Member] | ' | ' |
Debt Instrument [Line Items] | ' | ' |
Notes payable | 125,000 | 125,000 |
Carrying Amount [Member] | Debentures [Member] | Notes, 3.875%, due 2022 [Member] | ' | ' |
Debt Instrument [Line Items] | ' | ' |
Notes payable | 250,000 | 250,000 |
Carrying Amount [Member] | Debentures [Member] | Notes, 4.875%, due 2043 [Member] | ' | ' |
Debt Instrument [Line Items] | ' | ' |
Notes payable | 250,000 | 250,000 |
Carrying Amount [Member] | Debentures [Member] | 8% Series, due 2026 [Member] | ' | ' |
Debt Instrument [Line Items] | ' | ' |
Notes payable | 75,000 | 75,000 |
Carrying Amount [Member] | Debentures [Member] | Medium-term notes, 7.59% series, due 2017 [Member] | ' | ' |
Debt Instrument [Line Items] | ' | ' |
Notes payable | 25,000 | 25,000 |
Carrying Amount [Member] | Debentures [Member] | Medium-term notes, 7.78% series, due 2022 [Member] | ' | ' |
Debt Instrument [Line Items] | ' | ' |
Notes payable | 25,000 | 25,000 |
Carrying Amount [Member] | Debentures [Member] | Medium-term notes, 7.92% series, due 2027 [Member] | ' | ' |
Debt Instrument [Line Items] | ' | ' |
Notes payable | 25,000 | 25,000 |
Carrying Amount [Member] | Debentures [Member] | Medium-term notes, 6.76% series, due 2027 [Member] | ' | ' |
Debt Instrument [Line Items] | ' | ' |
Notes payable | 7,500 | 7,500 |
Carrying Amount [Member] | Debentures [Member] | Notes Payable [Member] | ' | ' |
Debt Instrument [Line Items] | ' | ' |
Notes payable | 902,022 | 901,940 |
Carrying Amount [Member] | Debentures [Member] | Revolving credit facility and commercial paper [Member] | ' | ' |
Debt Instrument [Line Items] | ' | ' |
Line of credit facility | ' | 10,000 |
Carrying Amount [Member] | Variable-rate bonds [Member] | Tax-exempt Series A, due 2028 [Member] | ' | ' |
Debt Instrument [Line Items] | ' | ' |
Unsecured debt | 50,000 | 50,000 |
Carrying Amount [Member] | Variable-rate bonds [Member] | 2003 Series A, due 2038 [Member] | ' | ' |
Debt Instrument [Line Items] | ' | ' |
Unsecured debt | 50,000 | 50,000 |
Carrying Amount [Member] | Variable-rate bonds [Member] | 2008 Series A, due 2038 [Member] | ' | ' |
Debt Instrument [Line Items] | ' | ' |
Unsecured debt | 50,000 | 50,000 |
Carrying Amount [Member] | Variable-rate bonds [Member] | 2009 Series A, due 2039 [Member] | ' | ' |
Debt Instrument [Line Items] | ' | ' |
Unsecured debt | 50,000 | 50,000 |
Carrying Amount [Member] | Fixed-rate bonds [Member] | 5.25% 2003 Series D, due 2038 [Member] | ' | ' |
Debt Instrument [Line Items] | ' | ' |
Unsecured debt | 20,000 | 20,000 |
Carrying Amount [Member] | Fixed-rate bonds [Member] | 5.25% 2004 Series A, due 2034 [Member] | ' | ' |
Debt Instrument [Line Items] | ' | ' |
Unsecured debt | 65,000 | 65,000 |
Carrying Amount [Member] | Fixed-rate bonds [Member] | 5.00% 2004 Series B, due 2033 [Member] | ' | ' |
Debt Instrument [Line Items] | ' | ' |
Unsecured debt | 31,200 | 31,200 |
Carrying Amount [Member] | Fixed-rate bonds [Member] | 4.85% 2005 Series A, due 2035 [Member] | ' | ' |
Debt Instrument [Line Items] | ' | ' |
Unsecured debt | 100,000 | 100,000 |
Carrying Amount [Member] | Fixed-rate bonds [Member] | 4.75% 2006 Series A, due 2036 [Member] | ' | ' |
Debt Instrument [Line Items] | ' | ' |
Unsecured debt | 24,855 | 24,855 |
Market Value [Member] | NPL other debt obligations [Member] | ' | ' |
Debt Instrument [Line Items] | ' | ' |
NPL other debt obligations | 39,465 | 42,119 |
Market Value [Member] | NPL credit facility [Member] | ' | ' |
Debt Instrument [Line Items] | ' | ' |
NPL credit facility | ' | ' |
Market Value [Member] | Debentures [Member] | Notes, 4.45%, due 2020 [Member] | ' | ' |
Debt Instrument [Line Items] | ' | ' |
Notes payable, fair value disclosure | 134,433 | 130,953 |
Market Value [Member] | Debentures [Member] | Notes, 6.1%, due 2041 [Member] | ' | ' |
Debt Instrument [Line Items] | ' | ' |
Notes payable, fair value disclosure | 148,894 | 141,873 |
Market Value [Member] | Debentures [Member] | Notes, 3.875%, due 2022 [Member] | ' | ' |
Debt Instrument [Line Items] | ' | ' |
Notes payable, fair value disclosure | 255,923 | 252,485 |
Market Value [Member] | Debentures [Member] | Notes, 4.875%, due 2043 [Member] | ' | ' |
Debt Instrument [Line Items] | ' | ' |
Notes payable, fair value disclosure | 268,873 | 257,280 |
Market Value [Member] | Debentures [Member] | 8% Series, due 2026 [Member] | ' | ' |
Debt Instrument [Line Items] | ' | ' |
Notes payable, fair value disclosure | 101,735 | 96,263 |
Market Value [Member] | Debentures [Member] | Medium-term notes, 7.59% series, due 2017 [Member] | ' | ' |
Debt Instrument [Line Items] | ' | ' |
Notes payable, fair value disclosure | 28,691 | 28,741 |
Market Value [Member] | Debentures [Member] | Medium-term notes, 7.78% series, due 2022 [Member] | ' | ' |
Debt Instrument [Line Items] | ' | ' |
Notes payable, fair value disclosure | 31,585 | 30,586 |
Market Value [Member] | Debentures [Member] | Medium-term notes, 7.92% series, due 2027 [Member] | ' | ' |
Debt Instrument [Line Items] | ' | ' |
Notes payable, fair value disclosure | 33,402 | 31,497 |
Market Value [Member] | Debentures [Member] | Medium-term notes, 6.76% series, due 2027 [Member] | ' | ' |
Debt Instrument [Line Items] | ' | ' |
Notes payable, fair value disclosure | 9,021 | 8,468 |
Market Value [Member] | Debentures [Member] | Revolving credit facility and commercial paper [Member] | ' | ' |
Debt Instrument [Line Items] | ' | ' |
Line of credit facility, fair value | ' | 10,000 |
Market Value [Member] | Variable-rate bonds [Member] | Tax-exempt Series A, due 2028 [Member] | ' | ' |
Debt Instrument [Line Items] | ' | ' |
Unsecured Debt Fair Value | 50,000 | 50,000 |
Market Value [Member] | Variable-rate bonds [Member] | 2003 Series A, due 2038 [Member] | ' | ' |
Debt Instrument [Line Items] | ' | ' |
Unsecured Debt Fair Value | 50,000 | 50,000 |
Market Value [Member] | Variable-rate bonds [Member] | 2008 Series A, due 2038 [Member] | ' | ' |
Debt Instrument [Line Items] | ' | ' |
Unsecured Debt Fair Value | 50,000 | 50,000 |
Market Value [Member] | Variable-rate bonds [Member] | 2009 Series A, due 2039 [Member] | ' | ' |
Debt Instrument [Line Items] | ' | ' |
Unsecured Debt Fair Value | 50,000 | 50,000 |
Market Value [Member] | Fixed-rate bonds [Member] | 5.25% 2003 Series D, due 2038 [Member] | ' | ' |
Debt Instrument [Line Items] | ' | ' |
Unsecured Debt Fair Value | 20,289 | 20,150 |
Market Value [Member] | Fixed-rate bonds [Member] | 5.25% 2004 Series A, due 2034 [Member] | ' | ' |
Debt Instrument [Line Items] | ' | ' |
Unsecured Debt Fair Value | 65,051 | 64,522 |
Market Value [Member] | Fixed-rate bonds [Member] | 5.00% 2004 Series B, due 2033 [Member] | ' | ' |
Debt Instrument [Line Items] | ' | ' |
Unsecured Debt Fair Value | 31,229 | 30,284 |
Market Value [Member] | Fixed-rate bonds [Member] | 4.85% 2005 Series A, due 2035 [Member] | ' | ' |
Debt Instrument [Line Items] | ' | ' |
Unsecured Debt Fair Value | 99,709 | 95,192 |
Market Value [Member] | Fixed-rate bonds [Member] | 4.75% 2006 Series A, due 2036 [Member] | ' | ' |
Debt Instrument [Line Items] | ' | ' |
Unsecured Debt Fair Value | $24,539 | $22,974 |
LongTerm_Debt_Schedule_of_Carr1
Long-Term Debt - Schedule of Carrying Amounts and Estimated Fair Values of Long-Term Debt (Parenthetical) (Detail) | 3 Months Ended | 12 Months Ended |
Mar. 31, 2014 | Dec. 31, 2013 | |
Notes, 6.1%, due 2041 [Member] | ' | ' |
Debt Instrument [Line Items] | ' | ' |
Debt instrument interest rate | 6.10% | ' |
Debentures [Member] | Carrying Amount [Member] | Notes, 4.45%, due 2020 [Member] | ' | ' |
Debt Instrument [Line Items] | ' | ' |
Debt instrument interest rate | 4.45% | 4.45% |
Debt instrument due date | 1-Dec-20 | 1-Dec-20 |
Debentures [Member] | Carrying Amount [Member] | Notes, 6.1%, due 2041 [Member] | ' | ' |
Debt Instrument [Line Items] | ' | ' |
Debt instrument interest rate | 6.10% | 6.10% |
Debt instrument due date | 15-Feb-41 | 15-Feb-41 |
Debentures [Member] | Carrying Amount [Member] | Notes, 3.875%, due 2022 [Member] | ' | ' |
Debt Instrument [Line Items] | ' | ' |
Debt instrument interest rate | 3.88% | 3.88% |
Debt instrument due date | 1-Apr-22 | 1-Apr-22 |
Debentures [Member] | Carrying Amount [Member] | Notes, 4.875%, due 2043 [Member] | ' | ' |
Debt Instrument [Line Items] | ' | ' |
Debt instrument interest rate | 4.88% | 4.88% |
Debt instrument due date | 1-Oct-43 | 1-Oct-43 |
Debentures [Member] | Carrying Amount [Member] | 8% Series, due 2026 [Member] | ' | ' |
Debt Instrument [Line Items] | ' | ' |
Debt instrument interest rate | 8.00% | 8.00% |
Debt instrument due date | 1-Aug-26 | 1-Aug-26 |
Debentures [Member] | Carrying Amount [Member] | Medium-term notes, 7.59% series, due 2017 [Member] | ' | ' |
Debt Instrument [Line Items] | ' | ' |
Debt instrument interest rate | 7.59% | 7.59% |
Debt instrument due date | 17-Jan-17 | 17-Jan-17 |
Debentures [Member] | Carrying Amount [Member] | Medium-term notes, 7.78% series, due 2022 [Member] | ' | ' |
Debt Instrument [Line Items] | ' | ' |
Debt instrument interest rate | 7.78% | 7.78% |
Debt instrument due date | 3-Feb-22 | 3-Feb-22 |
Debentures [Member] | Carrying Amount [Member] | Medium-term notes, 7.92% series, due 2027 [Member] | ' | ' |
Debt Instrument [Line Items] | ' | ' |
Debt instrument interest rate | 7.92% | 7.92% |
Debt instrument due date | 4-Jun-27 | 4-Jun-27 |
Debentures [Member] | Carrying Amount [Member] | Medium-term notes, 6.76% series, due 2027 [Member] | ' | ' |
Debt Instrument [Line Items] | ' | ' |
Debt instrument interest rate | 6.76% | 6.76% |
Debt instrument due date | 24-Sep-27 | 24-Sep-27 |
Debentures [Member] | Market Value [Member] | Notes, 4.45%, due 2020 [Member] | ' | ' |
Debt Instrument [Line Items] | ' | ' |
Debt instrument interest rate | 4.45% | 4.45% |
Debt instrument due date | 1-Dec-20 | 1-Dec-20 |
Debentures [Member] | Market Value [Member] | Notes, 6.1%, due 2041 [Member] | ' | ' |
Debt Instrument [Line Items] | ' | ' |
Debt instrument interest rate | 6.10% | 6.10% |
Debt instrument due date | 15-Feb-41 | 15-Feb-41 |
Debentures [Member] | Market Value [Member] | Notes, 3.875%, due 2022 [Member] | ' | ' |
Debt Instrument [Line Items] | ' | ' |
Debt instrument interest rate | 3.88% | 3.88% |
Debt instrument due date | 1-Apr-22 | 1-Apr-22 |
Debentures [Member] | Market Value [Member] | Notes, 4.875%, due 2043 [Member] | ' | ' |
Debt Instrument [Line Items] | ' | ' |
Debt instrument interest rate | 4.88% | 4.88% |
Debt instrument due date | 1-Oct-43 | 1-Oct-43 |
Debentures [Member] | Market Value [Member] | 8% Series, due 2026 [Member] | ' | ' |
Debt Instrument [Line Items] | ' | ' |
Debt instrument interest rate | 8.00% | 8.00% |
Debt instrument due date | 1-Aug-26 | 1-Aug-26 |
Debentures [Member] | Market Value [Member] | Medium-term notes, 7.59% series, due 2017 [Member] | ' | ' |
Debt Instrument [Line Items] | ' | ' |
Debt instrument interest rate | 7.59% | 7.59% |
Debt instrument due date | 17-Jan-17 | 17-Jan-17 |
Debentures [Member] | Market Value [Member] | Medium-term notes, 7.78% series, due 2022 [Member] | ' | ' |
Debt Instrument [Line Items] | ' | ' |
Debt instrument interest rate | 7.78% | 7.78% |
Debt instrument due date | 3-Feb-22 | 3-Feb-22 |
Debentures [Member] | Market Value [Member] | Medium-term notes, 7.92% series, due 2027 [Member] | ' | ' |
Debt Instrument [Line Items] | ' | ' |
Debt instrument interest rate | 7.92% | 7.92% |
Debt instrument due date | 4-Jun-27 | 4-Jun-27 |
Debentures [Member] | Market Value [Member] | Medium-term notes, 6.76% series, due 2027 [Member] | ' | ' |
Debt Instrument [Line Items] | ' | ' |
Debt instrument interest rate | 6.76% | 6.76% |
Debt instrument due date | 24-Sep-27 | 24-Sep-27 |
Variable-rate bonds [Member] | Carrying Amount [Member] | Tax-exempt Series A, due 2028 [Member] | ' | ' |
Debt Instrument [Line Items] | ' | ' |
Debt instrument due date | 1-Dec-28 | 1-Dec-28 |
Variable-rate bonds [Member] | Carrying Amount [Member] | 2003 Series A, due 2038 [Member] | ' | ' |
Debt Instrument [Line Items] | ' | ' |
Debt instrument due date | 1-Mar-38 | 1-Mar-38 |
Variable-rate bonds [Member] | Carrying Amount [Member] | 2008 Series A, due 2038 [Member] | ' | ' |
Debt Instrument [Line Items] | ' | ' |
Debt instrument due date | 1-Mar-38 | 1-Mar-38 |
Variable-rate bonds [Member] | Carrying Amount [Member] | 2009 Series A, due 2039 [Member] | ' | ' |
Debt Instrument [Line Items] | ' | ' |
Debt instrument due date | 1-Dec-39 | 1-Dec-39 |
Variable-rate bonds [Member] | Market Value [Member] | Tax-exempt Series A, due 2028 [Member] | ' | ' |
Debt Instrument [Line Items] | ' | ' |
Debt instrument due date | 1-Dec-28 | 1-Dec-28 |
Variable-rate bonds [Member] | Market Value [Member] | 2003 Series A, due 2038 [Member] | ' | ' |
Debt Instrument [Line Items] | ' | ' |
Debt instrument due date | 1-Mar-38 | 1-Mar-38 |
Variable-rate bonds [Member] | Market Value [Member] | 2008 Series A, due 2038 [Member] | ' | ' |
Debt Instrument [Line Items] | ' | ' |
Debt instrument due date | 1-Mar-38 | 1-Mar-38 |
Variable-rate bonds [Member] | Market Value [Member] | 2009 Series A, due 2039 [Member] | ' | ' |
Debt Instrument [Line Items] | ' | ' |
Debt instrument due date | 1-Dec-39 | 1-Dec-39 |
Fixed-rate bonds [Member] | Carrying Amount [Member] | 5.25% 2003 Series D, due 2038 [Member] | ' | ' |
Debt Instrument [Line Items] | ' | ' |
Debt instrument interest rate | 5.25% | 5.25% |
Debt instrument due date | 1-Dec-38 | 1-Dec-38 |
Fixed-rate bonds [Member] | Carrying Amount [Member] | 5.25% 2004 Series A, due 2034 [Member] | ' | ' |
Debt Instrument [Line Items] | ' | ' |
Debt instrument interest rate | 5.25% | 5.25% |
Debt instrument due date | 1-Jul-34 | 1-Jul-34 |
Fixed-rate bonds [Member] | Carrying Amount [Member] | 5.00% 2004 Series B, due 2033 [Member] | ' | ' |
Debt Instrument [Line Items] | ' | ' |
Debt instrument interest rate | 5.00% | 5.00% |
Debt instrument due date | 1-Dec-33 | 1-Dec-33 |
Fixed-rate bonds [Member] | Carrying Amount [Member] | 4.85% 2005 Series A, due 2035 [Member] | ' | ' |
Debt Instrument [Line Items] | ' | ' |
Debt instrument interest rate | 4.85% | 4.85% |
Debt instrument due date | 1-Oct-35 | 1-Oct-35 |
Fixed-rate bonds [Member] | Carrying Amount [Member] | 4.75% 2006 Series A, due 2036 [Member] | ' | ' |
Debt Instrument [Line Items] | ' | ' |
Debt instrument interest rate | 4.75% | 4.75% |
Debt instrument due date | 1-Sep-36 | 1-Sep-36 |
Fixed-rate bonds [Member] | Market Value [Member] | 5.25% 2003 Series D, due 2038 [Member] | ' | ' |
Debt Instrument [Line Items] | ' | ' |
Debt instrument interest rate | 5.25% | 5.25% |
Debt instrument due date | 1-Dec-38 | 1-Dec-38 |
Fixed-rate bonds [Member] | Market Value [Member] | 5.25% 2004 Series A, due 2034 [Member] | ' | ' |
Debt Instrument [Line Items] | ' | ' |
Debt instrument interest rate | 5.25% | 5.25% |
Debt instrument due date | 1-Jul-34 | 1-Jul-34 |
Fixed-rate bonds [Member] | Market Value [Member] | 5.00% 2004 Series B, due 2033 [Member] | ' | ' |
Debt Instrument [Line Items] | ' | ' |
Debt instrument interest rate | 5.00% | 5.00% |
Debt instrument due date | 1-Dec-33 | 1-Dec-33 |
Fixed-rate bonds [Member] | Market Value [Member] | 4.85% 2005 Series A, due 2035 [Member] | ' | ' |
Debt Instrument [Line Items] | ' | ' |
Debt instrument interest rate | 4.85% | 4.85% |
Debt instrument due date | 1-Oct-35 | 1-Oct-35 |
Fixed-rate bonds [Member] | Market Value [Member] | 4.75% 2006 Series A, due 2036 [Member] | ' | ' |
Debt Instrument [Line Items] | ' | ' |
Debt instrument interest rate | 4.75% | 4.75% |
Debt instrument due date | 1-Sep-36 | 1-Sep-36 |
LongTerm_Debt_Additional_Infor
Long-Term Debt - Additional Information (Detail) (USD $) | 3 Months Ended |
Mar. 31, 2014 | |
Debt Instrument [Line Items] | ' |
Line of credit designated as long term debt | $150,000,000 |
Line of credit designated for working capital purposes | 150,000,000 |
Two Thousand And Nineteen [Member] | ' |
Debt Instrument [Line Items] | ' |
Credit facility maximum borrowing capacity | 300,000,000 |
Credit facility expiration date | 1-Mar-19 |
LIBOR [Member] | Southwest Gas Credit Facility [Member] | ' |
Debt Instrument [Line Items] | ' |
Applicable margin | 1.00% |
Alternative base rate [Member] | Southwest Gas Credit Facility [Member] | ' |
Debt Instrument [Line Items] | ' |
Applicable margin | 0.00% |
Notes, 6.1%, due 2041 [Member] | ' |
Debt Instrument [Line Items] | ' |
Debt instrument interest rate | 6.10% |
Notes payable | $125,000,000 |
Notes, 6.1%, due 2041 [Member] | Maximum [Member] | ' |
Debt Instrument [Line Items] | ' |
Percentage limit on liens securing indebtedness | 10.00% |
Equity_Other_Comprehensive_Inc2
Equity, Other Comprehensive Income, and Accumulated Other Comprehensive Income - Detailed Activities of Equity (Detail) (USD $) | 3 Months Ended | 12 Months Ended | ||
In Thousands, except Share data, unless otherwise specified | Mar. 31, 2014 | Mar. 31, 2013 | Mar. 31, 2014 | Mar. 31, 2013 |
Schedule Of Stockholders Equity [Line Items] | ' | ' | ' | ' |
Balance | $1,412,395 | ' | ' | ' |
Balance, shares | 46,356,125 | ' | ' | ' |
Common stock issuances | 3,081 | ' | ' | ' |
Net income (loss) | 70,697 | 80,674 | 134,896 | 134,478 |
Other comprehensive income (loss): | ' | ' | ' | ' |
Net actuarial gain (loss) arising during period, less amortization of unamortized benefit plan cost, net of tax | 512 | 651 | 6,834 | -4,810 |
Amounts reclassified into net income | 518 | 518 | 2,074 | 2,074 |
Dividends declared Common: $0.365 per share | -17,193 | ' | ' | ' |
Balance | 1,470,010 | ' | 1,470,010 | ' |
Balance, shares | 46,495,191 | ' | 46,495,191 | ' |
Common Stock [Member] | ' | ' | ' | ' |
Schedule Of Stockholders Equity [Line Items] | ' | ' | ' | ' |
Balance | 47,986 | ' | ' | ' |
Balance, shares | 46,356,000 | ' | ' | ' |
Common stock issuances | 139 | ' | ' | ' |
Common stock issuances, shares | 139 | ' | ' | ' |
Other comprehensive income (loss): | ' | ' | ' | ' |
Balance | 48,125 | ' | 48,125 | ' |
Balance, shares | 46,495,000 | ' | 46,495,000 | ' |
Additional Paid-in Capital [Member] | ' | ' | ' | ' |
Schedule Of Stockholders Equity [Line Items] | ' | ' | ' | ' |
Balance | 840,521 | ' | ' | ' |
Common stock issuances | 2,942 | ' | ' | ' |
Other comprehensive income (loss): | ' | ' | ' | ' |
Balance | 843,463 | ' | 843,463 | ' |
Accumulated Other Comprehensive Income (Loss) [Member] | ' | ' | ' | ' |
Schedule Of Stockholders Equity [Line Items] | ' | ' | ' | ' |
Balance | -41,698 | ' | ' | ' |
Other comprehensive income (loss): | ' | ' | ' | ' |
Net actuarial gain (loss) arising during period, less amortization of unamortized benefit plan cost, net of tax | 512 | ' | ' | ' |
Amounts reclassified into net income | 518 | ' | ' | ' |
Balance | -40,668 | ' | -40,668 | ' |
Retained Earnings [Member] | ' | ' | ' | ' |
Schedule Of Stockholders Equity [Line Items] | ' | ' | ' | ' |
Balance | 567,714 | ' | ' | ' |
Net income (loss) | 70,783 | ' | ' | ' |
Other comprehensive income (loss): | ' | ' | ' | ' |
Dividends declared Common: $0.365 per share | -17,193 | ' | ' | ' |
Balance | 621,304 | ' | 621,304 | ' |
Non-controlling Interest [Member] | ' | ' | ' | ' |
Schedule Of Stockholders Equity [Line Items] | ' | ' | ' | ' |
Balance | -2,128 | ' | ' | ' |
Net income (loss) | -86 | ' | ' | ' |
Other comprehensive income (loss): | ' | ' | ' | ' |
Balance | ($2,214) | ' | ($2,214) | ' |
Equity_Other_Comprehensive_Inc3
Equity, Other Comprehensive Income, and Accumulated Other Comprehensive Income - Detailed Activities of Equity (Parenthetical) (Detail) (USD $) | 3 Months Ended | 12 Months Ended | ||
Mar. 31, 2014 | Mar. 31, 2013 | Mar. 31, 2014 | Mar. 31, 2013 | |
Statement Of Stockholders Equity [Abstract] | ' | ' | ' | ' |
Dividends declared per share | $0.37 | $0.33 | $1.36 | $1.22 |
Equity_Other_Comprehensive_Inc4
Equity, Other Comprehensive Income, and Accumulated Other Comprehensive Income - Related Tax Effects Allocated to Each Component of Other Comprehensive Income (Loss) (Detail) (USD $) | 3 Months Ended | 12 Months Ended | ||
In Thousands, unless otherwise specified | Mar. 31, 2014 | Mar. 31, 2013 | Mar. 31, 2014 | Mar. 31, 2013 |
Equity [Abstract] | ' | ' | ' | ' |
Amortization of net actuarial (gain)/loss, Before-Tax Amount | $5,914 | $8,545 | $31,546 | $27,742 |
Amortization of prior service cost, Before-Tax Amount | 89 | 89 | 355 | 89 |
Regulatory adjustment, Before-Tax Amount | -5,178 | -7,584 | -121,224 | 41,036 |
Pension plans other comprehensive income (loss), Before-Tax Amount | 825 | 1,050 | 11,022 | -7,759 |
Amounts reclassified into net income, Before-Tax Amount | 836 | 836 | 3,345 | 3,345 |
FSIRS other comprehensive income (loss), Before-Tax Amount | 836 | 836 | 3,345 | 3,345 |
Total other comprehensive income (loss), Before-Tax Amount | 1,661 | 1,886 | 14,367 | -4,414 |
Amortization of net actuarial (gain)/loss, Tax (Expense) or Benefit | -2,247 | -3,247 | -11,987 | -10,542 |
Amortization of prior service cost, Tax (Expense) or Benefit | -34 | -34 | -135 | -34 |
Regulatory adjustment, Tax (Expense) or Benefit | 1,968 | 2,882 | 46,065 | -15,594 |
Pension plans other comprehensive income (loss), Tax (Expense) or Benefit | -313 | -399 | -4,188 | 2,949 |
Amounts reclassified into net income, Tax (Expense) or Benefit | -318 | -318 | -1,271 | -1,271 |
FSIRS other comprehensive income (loss), Tax (Expense) or Benefit | -318 | -318 | -1,271 | -1,271 |
Total other comprehensive income (loss), Tax (Expense) or Benefit | -631 | -717 | -5,459 | 1,678 |
Amortization of net actuarial (gain)/loss), Net-of-Tax Amount | 3,667 | 5,298 | 19,559 | 17,200 |
Amortization of prior service cost, Net-of-Tax Amount | 55 | 55 | 220 | 55 |
Regulatory adjustment, Net-of-Tax Amount | -3,210 | -4,702 | -75,159 | 25,442 |
Net defined benefit pension plans | 512 | 651 | 6,834 | -4,810 |
Amounts reclassified into net income | 518 | 518 | 2,074 | 2,074 |
FSIRS other comprehensive income (loss), Net-of-Tax Amount | 518 | 518 | 2,074 | 2,074 |
Total other comprehensive income (loss), Net-of-Tax Amount | 1,030 | 1,169 | 8,908 | -2,736 |
Net actuarial gain/(loss), Before-Tax Amount | ' | ' | 100,345 | -74,853 |
Amortization of transition obligation, Before-Tax Amount | ' | ' | ' | 650 |
Prior service cost, Before-Tax Amount | ' | ' | ' | -2,423 |
Net actuarial gain/(loss), Tax (Expense) or Benefit | ' | ' | -38,131 | 28,444 |
Amortization of transition obligation, Tax (Expense) or Benefit | ' | ' | ' | -246 |
Prior service cost, Tax (Expense) or Benefit | ' | ' | ' | 921 |
Net actuarial gain/(loss), Net-of-Tax Amount | ' | ' | 62,214 | -46,409 |
Amortization of transition obligation, Net-of-Tax Amount | ' | ' | ' | 404 |
Prior service cost, Net-of-Tax Amount | ' | ' | ' | ($1,502) |
Equity_Other_Comprehensive_Inc5
Equity, Other Comprehensive Income, and Accumulated Other Comprehensive Income - Related Tax Effects Allocated to Each Component of Other Comprehensive Income (Loss) (Parenthetical) (Detail) | 3 Months Ended |
Mar. 31, 2014 | |
Equity [Abstract] | ' |
Other comprehensive income loss, effective income tax rate | 38.00% |
Equity_Other_Comprehensive_Inc6
Equity, Other Comprehensive Income, and Accumulated Other Comprehensive Income - Additional Information (Detail) (USD $) | Mar. 31, 2014 |
In Millions, unless otherwise specified | |
Equity [Abstract] | ' |
Amount of FSIRS existing AOCI losses expected to reclassified income in next 12 months | $2.10 |
Equity_Other_Comprehensive_Inc7
Equity, Other Comprehensive Income, and Accumulated Other Comprehensive Income - Rollforward of Accumulated Other Comprehensive Income (Detail) (USD $) | 3 Months Ended | 12 Months Ended | ||
In Thousands, unless otherwise specified | Mar. 31, 2014 | Mar. 31, 2013 | Mar. 31, 2014 | Mar. 31, 2013 |
Schedule Of Stockholders Equity [Line Items] | ' | ' | ' | ' |
Beginning Balance AOCI December 31, 2013, Defined Benefit Plans Before-Tax | ($41,223) | ' | ' | ' |
Amortization of prior service cost, Defined Benefit Plans Before-Tax | 89 | 89 | 355 | 89 |
Amortization of net actuarial loss, Defined Benefit Plans Before-Tax | 5,914 | 8,545 | 31,546 | 27,742 |
Regulatory adjustment, Defined Benefit Plans Before-Tax | -5,178 | -7,584 | -121,224 | 41,036 |
Net current period other comprehensive income (loss), Defined Benefit Plans Before-Tax | 825 | 1,050 | 11,022 | -7,759 |
Ending Balance AOCI March 31, 2014, Defined Benefit Plans Before-Tax | -40,398 | ' | -40,398 | ' |
Beginning Balance AOCI December 31, 2013, Defined Benefit Plans Tax (Expense) Benefit | 15,665 | ' | ' | ' |
Amortization of prior service costs, Defined Benefit Plans Tax (Expense) Benefit | -34 | -34 | -135 | -34 |
Amortization of net actuarial loss, Defined Benefit Plans Tax (Expense) Benefit | -2,247 | -3,247 | -11,987 | -10,542 |
Regulatory adjustment, Defined Benefit Plans Tax (Expense) Benefit | 1,968 | 2,882 | 46,065 | -15,594 |
Net current period other comprehensive income (loss), Defined Benefit Plans Tax (Expense) Benefit | -313 | -399 | -4,188 | 2,949 |
Ending Balance AOCI March 31, 2013 Defined Benefit Plans Tax (Expense) Benefit | 15,352 | ' | 15,352 | ' |
Beginning Balance AOCI December 31, 2013, Defined Benefit Plans After-Tax | -25,558 | ' | ' | ' |
Amortization of prior service costs, Defined Benefit Plans After-Tax | 55 | 55 | 220 | 55 |
Amortization of net actuarial (gain)/loss), Net-of-Tax Amount | 3,667 | 5,298 | 19,559 | 17,200 |
Regulatory adjustment, AOCI | -3,210 | -4,702 | -75,159 | 25,442 |
Net current period other comprehensive income (loss), Defined Benefit Plans After-Tax | 512 | 651 | 6,834 | -4,810 |
Ending Balance AOCI March 31, 2014, Defined Benefit Plans After-Tax | -25,046 | ' | -25,046 | ' |
Beginning Balance AOCI December 31, 2013, FSIRS - Before-Tax | -26,033 | ' | ' | ' |
FSIRS amounts reclassified from AOCI, FSIRS - Before-Tax | 836 | 836 | 3,345 | 3,345 |
FSIRS amounts reclassified from AOCI, FSIRS - Tax (Expense) Benefit | -318 | -318 | -1,271 | -1,271 |
Ending Balance AOCI March 31, 2014, FSIRS - Before-Tax | -25,197 | ' | -25,197 | ' |
Beginning Balance AOCI December 31, 2013, FSIRS - Tax (Expense) Benefit | 9,893 | ' | ' | ' |
Net current period other comprehensive income (loss), FSIRS - Tax (Expense) Benefit | -318 | -318 | -1,271 | -1,271 |
Ending Balance AOCI March 31, 2014, FSIRS - Tax (Expense) Benefit | 9,575 | ' | 9,575 | ' |
Beginning Balance AOCI December 31, 2013, FSIRS - After-Tax | -16,140 | ' | ' | ' |
FSIRS amounts reclassified from AOCI, FSIRS - After-Tax | 518 | 518 | 2,074 | 2,074 |
Net forward-starting interest rate swaps | 518 | 518 | 2,074 | 2,074 |
Ending Balance AOCI March 31, 2014, FSIRS - After-Tax | -15,622 | ' | -15,622 | ' |
Beginning Balance AOCI December 31, 2013, AOCI | -41,698 | ' | ' | ' |
Amounts reclassified into net income | 518 | 518 | 2,074 | 2,074 |
Amortization of prior service costs, AOCI | 55 | 55 | 220 | 55 |
Amortization of net actuarial loss | 3,667 | 5,298 | 19,559 | 17,200 |
Regulatory adjustment, Net-of-Tax Amount | -3,210 | -4,702 | -75,159 | 25,442 |
Net current period other comprehensive income (loss), AOCI | 1,030 | ' | ' | ' |
Ending Balance AOCI March 31, 2014, AOCI | -40,668 | ' | -40,668 | ' |
Reclassification out of Accumulated Other Comprehensive Income [Member] | ' | ' | ' | ' |
Schedule Of Stockholders Equity [Line Items] | ' | ' | ' | ' |
Other comprehensive income before reclassifications, FSIRS - Tax (Expense) Benefit | ' | ' | ' | ' |
Other comprehensive income before reclassifications, Defined Benefit Plans Before-Tax | ' | ' | ' | ' |
Other comprehensive income before reclassifications, Defined Benefit Plans Tax (Expense) Benefit | ' | ' | ' | ' |
Other comprehensive income before reclassifications, Defined Benefit Plans After-Tax | ' | ' | ' | ' |
Other comprehensive income before reclassifications, FSIRS - Before-Tax | ' | ' | ' | ' |
FSIRS amounts reclassified from AOCI, FSIRS - Before-Tax | 836 | ' | ' | ' |
FSIRS amounts reclassified from AOCI, FSIRS - Tax (Expense) Benefit | 318 | ' | ' | ' |
Other comprehensive income before reclassifications, FSIRS - After-Tax | ' | ' | ' | ' |
FSIRS amounts reclassified from AOCI, FSIRS - After-Tax | 518 | ' | ' | ' |
Other comprehensive income before reclassifications, AOCI | ' | ' | ' | ' |
Amounts reclassified into net income | $518 | ' | ' | ' |
Equity_Other_Comprehensive_Inc8
Equity, Other Comprehensive Income, and Accumulated Other Comprehensive Income - Amount Recognized Before Income Tax in Accumulated Other Comprehensive Income (Detail) (USD $) | 12 Months Ended | 3 Months Ended | 12 Months Ended | ||
In Thousands, unless otherwise specified | Mar. 31, 2013 | Mar. 31, 2014 | Dec. 31, 2013 | Mar. 31, 2014 | Dec. 31, 2013 |
Defined Benefit Plans [Member] | Defined Benefit Plans [Member] | ||||
Accumulated Other Comprehensive Income (Loss) [Line Items] | ' | ' | ' | ' | ' |
Net actuarial (loss) gain | ' | ' | ' | ($283,227) | ($289,141) |
Prior service cost | 2,423 | ' | ' | -1,978 | -2,067 |
Less: amount recognized in regulatory assets | ' | ' | ' | 244,807 | 249,985 |
Recognized in AOCI | ' | ($40,398) | ($41,223) | ($40,398) | ($41,223) |