Document and Entity Information
Document and Entity Information - USD ($) | 12 Months Ended | ||
Dec. 31, 2016 | Feb. 15, 2017 | Jun. 30, 2016 | |
Document And Entity Information [Abstract] | |||
Document Type | 10-K | ||
Amendment Flag | false | ||
Document Period End Date | Dec. 31, 2016 | ||
Document Fiscal Year Focus | 2,016 | ||
Document Fiscal Period Focus | FY | ||
Trading Symbol | SWX | ||
Entity Registrant Name | SOUTHWEST GAS CORP | ||
Entity Central Index Key | 92,416 | ||
Current Fiscal Year End Date | --12-31 | ||
Entity Well-known Seasoned Issuer | Yes | ||
Entity Current Reporting Status | Yes | ||
Entity Voluntary Filers | No | ||
Entity Filer Category | Large Accelerated Filer | ||
Entity Common Stock, Shares Outstanding | 47,546,825 | ||
Entity Public Float | $ 3,736,883,501 |
Consolidated Balance Sheets
Consolidated Balance Sheets - USD ($) | Dec. 31, 2016 | Dec. 31, 2015 |
Utility plant: | ||
Gas plant | $ 6,193,564,000 | $ 5,854,917,000 |
Less: accumulated depreciation | (2,172,966,000) | (2,084,007,000) |
Acquisition adjustments, net | 196,000 | 370,000 |
Construction work in progress | 111,177,000 | 119,805,000 |
Net utility plant (Note 2) | 4,131,971,000 | 3,891,085,000 |
Other property and investments (Note 1) | 342,343,000 | 313,531,000 |
Current assets: | ||
Cash and cash equivalents | 28,066,000 | 35,997,000 |
Accounts receivable, net of allowances (Note 3) | 285,145,000 | 314,512,000 |
Accrued utility revenue | 76,200,000 | 74,700,000 |
Income taxes receivable, net | 4,455,000 | 34,175,000 |
Deferred purchased gas costs (Note 4) | 2,608,000 | 3,591,000 |
Prepaids and other current assets (Notes 1, 4, and 13) | 136,833,000 | 95,199,000 |
Total current assets | 533,307,000 | 558,174,000 |
Noncurrent assets: | ||
Goodwill (Note 1) | 139,983,000 | 126,145,000 |
Deferred income taxes (Note 12) | 1,288,000 | 428,000 |
Deferred charges and other assets (Notes 2, 4, and 13) | 432,234,000 | 469,322,000 |
Total noncurrent assets | 573,505,000 | 595,895,000 |
Total assets | 5,581,126,000 | 5,358,685,000 |
Capitalization: | ||
Common stock, $1 par (authorized - 60,000,000 shares; issued and outstanding - 47,482,068 and 47,377,575 shares) (Note 11) | 49,112,000 | 49,007,000 |
Additional paid-in capital | 903,123,000 | 896,448,000 |
Accumulated other comprehensive income (loss), net (Note 5) | (48,008,000) | (50,268,000) |
Retained earnings | 759,263,000 | 699,221,000 |
Total Southwest Gas Corporation equity | 1,663,490,000 | 1,594,408,000 |
Noncontrolling interest | (2,217,000) | (2,083,000) |
Total equity | 1,661,273,000 | 1,592,325,000 |
Redeemable noncontrolling interest (Note 16) | 22,590,000 | 16,108,000 |
Long-term debt, less current maturities (Note 7) | 1,549,983,000 | 1,551,204,000 |
Total capitalization | 3,233,846,000 | 3,159,637,000 |
Commitments and contingencies (Note 9) | ||
Current liabilities: | ||
Current maturities of long-term debt (Note 7) | 50,101,000 | 19,475,000 |
Short-term debt (Note 8) | 0 | 18,000,000 |
Accounts payable | 184,669,000 | 164,857,000 |
Customer deposits | 72,296,000 | 72,631,000 |
Income taxes payable, net | 1,909,000 | 940,000 |
Accrued general taxes | 42,921,000 | 47,337,000 |
Accrued interest | 17,939,000 | 16,173,000 |
Deferred purchased gas costs (Note 4) | 90,476,000 | 45,601,000 |
Other current liabilities (Notes 2, 4, and 13) | 168,064,000 | 150,031,000 |
Total current liabilities | 628,375,000 | 535,045,000 |
Deferred income taxes and other credits: | ||
Deferred income taxes and investment tax credits, net (Note 12) | 840,653,000 | 769,445,000 |
Accumulated removal costs (Note 4) | 308,000,000 | 303,000,000 |
Other deferred credits and other long-term liabilities (Notes 2, 4, 10, and 13) | 570,252,000 | 591,558,000 |
Total deferred income taxes and other credits | 1,718,905,000 | 1,664,003,000 |
Total capitalization and liabilities | $ 5,581,126,000 | $ 5,358,685,000 |
Consolidated Balance Sheets (Pa
Consolidated Balance Sheets (Parenthetical) - $ / shares | Dec. 31, 2016 | Dec. 31, 2015 |
Statement of Financial Position [Abstract] | ||
Common stock, par | $ 1 | $ 1 |
Common stock, authorized | 60,000,000 | 60,000,000 |
Common stock, issued | 47,482,068 | 47,377,575 |
Common stock, outstanding | 47,482,068 | 47,377,575 |
Consolidated Statements of Inco
Consolidated Statements of Income - USD ($) shares in Thousands, $ in Thousands | 12 Months Ended | ||
Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2014 | |
Operating revenues: | |||
Gas operating revenues | $ 1,321,412 | $ 1,454,639 | $ 1,382,087 |
Construction revenues | 1,139,078 | 1,008,986 | 739,620 |
Total operating revenues | 2,460,490 | 2,463,625 | 2,121,707 |
Operating expenses: | |||
Net cost of gas sold | 397,121 | 563,809 | 505,356 |
Operations and maintenance | 401,724 | 393,199 | 383,732 |
Depreciation and amortization | 289,132 | 270,111 | 253,027 |
Taxes other than income taxes | 52,376 | 49,393 | 47,252 |
Construction expenses | 1,024,423 | 898,781 | 647,857 |
Total operating expenses | 2,164,776 | 2,175,293 | 1,837,224 |
Operating income | 295,714 | 288,332 | 284,483 |
Other income and (expenses): | |||
Net interest deductions (Notes 7 and 8) | (73,660) | (71,879) | (72,069) |
Other income (deductions) | 9,469 | 2,879 | 7,107 |
Total other income and (expenses) | (64,191) | (69,000) | (64,962) |
Income before income taxes | 231,523 | 219,332 | 219,521 |
Income tax expense (Note 12) | 78,468 | 79,902 | 78,373 |
Net income | 153,055 | 139,430 | 141,148 |
Net income (loss) attributable to noncontrolling interests | 1,014 | 1,113 | 22 |
Net income attributable to Southwest Gas Corporation | $ 152,041 | $ 138,317 | $ 141,126 |
Basic earnings per share (Notes 1 and 15) | $ 3.20 | $ 2.94 | $ 3.04 |
Diluted earnings per share (Notes 1 and 15) | $ 3.18 | $ 2.92 | $ 3.01 |
Average number of common shares outstanding | 47,469 | 46,992 | 46,494 |
Average shares outstanding (assuming dilution) | 47,814 | 47,383 | 46,944 |
Consolidated Statements of Comp
Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands | 12 Months Ended | ||
Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2014 | |
Statement of Comprehensive Income [Abstract] | |||
Net Income | $ 153,055 | $ 139,430 | $ 141,148 |
Defined benefit pension plans (Notes 5 and 10): | |||
Net actuarial gain (loss) | (14,118) | (18,922) | (107,661) |
Amortization of prior service cost | 828 | 828 | 220 |
Amortization of net actuarial loss | 16,781 | 21,316 | 14,667 |
Prior service cost | 0 | 0 | (4,130) |
Regulatory adjustment | (3,462) | (3,500) | 86,991 |
Net defined benefit pension plans | 29 | (278) | (9,913) |
Forward-starting interest rate swaps: | |||
Amounts reclassified into net income (Notes 5 and 13) | 2,075 | 2,073 | 2,073 |
Net forward-starting interest rate swaps | 2,075 | 2,073 | 2,073 |
Foreign currency translation adjustments | 161 | (1,954) | (659) |
Total other comprehensive income (loss), net of tax | 2,265 | (159) | (8,499) |
Comprehensive income | 155,320 | 139,271 | 132,649 |
Comprehensive income (loss) attributable to noncontrolling interests | 1,019 | 1,047 | 0 |
Comprehensive income attributable to Southwest Gas Corporation | $ 154,301 | $ 138,224 | $ 132,649 |
Consolidated Statements of Cash
Consolidated Statements of Cash Flows - USD ($) $ in Thousands | 12 Months Ended | ||
Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2014 | |
CASH FLOW FROM OPERATING ACTIVITIES: | |||
Net Income | $ 153,055 | $ 139,430 | $ 141,148 |
Adjustments to reconcile net income to net cash provided by operating activities: | |||
Depreciation and amortization | 289,132 | 270,111 | 253,027 |
Deferred income taxes | 68,732 | 48,785 | 64,309 |
Changes in current assets and liabilities: | |||
Accounts receivable, net of allowances | 30,096 | (39,850) | (3,683) |
Accrued utility revenue | (1,500) | (800) | (1,200) |
Deferred purchased gas costs | 45,858 | 129,566 | (69,339) |
Accounts payable | 21,695 | (3,491) | (41,499) |
Accrued taxes | 26,340 | (8,405) | (13,573) |
Other current assets and liabilities | (29,551) | 18,300 | 23,379 |
Gains on sale | (7,148) | (3,102) | (6,171) |
Changes in undistributed stock compensation | 5,456 | 2,914 | 7,973 |
AFUDC | (2,289) | (3,008) | (1,995) |
Changes in other assets and deferred charges | 16,960 | (14,166) | (21,732) |
Changes in other liabilities and deferred credits | (18,447) | 10,863 | 15,779 |
Net cash provided by operating activities | 598,389 | 547,147 | 346,423 |
CASH FLOW FROM INVESTING ACTIVITIES: | |||
Construction expenditures and property additions | (529,531) | (488,000) | (396,898) |
Acquisition of businesses, net of cash acquired | (17,000) | (9,261) | (190,497) |
Restricted cash | 0 | 785 | 1,233 |
Changes in customer advances | 7,900 | 18,300 | 20,363 |
Miscellaneous inflows | 13,039 | 8,354 | 11,611 |
Miscellaneous outflows | 0 | 0 | (1,400) |
Net cash used in investing activities | (525,592) | (469,822) | (555,588) |
CASH FLOW FROM FINANCING ACTIVITIES: | |||
Issuance of common stock, net | 472 | 35,396 | 405 |
Dividends paid | (83,317) | (74,248) | (66,275) |
Centuri distribution to redeemable noncontrolling interest | (439) | (99) | 0 |
Issuance of long-term debt, net | 423,946 | 135,816 | 269,228 |
Retirement of long-term debt | (255,273) | (187,973) | (139,155) |
Change in credit facility and commercial paper | (145,000) | 0 | 140,000 |
Change in short-term debt | (18,000) | 13,000 | 5,000 |
Principal payments on capital lease obligations | (1,354) | (1,420) | (434) |
Other | (1,569) | 41 | (1,257) |
Net cash provided by (used in) financing activities | (80,534) | (79,487) | 207,512 |
Effects of currency translation on cash and cash equivalents | (194) | (1,407) | 142 |
Change in cash and cash equivalents | (7,931) | (3,569) | (1,511) |
Cash and cash equivalents at beginning of period | 35,997 | 39,566 | 41,077 |
Cash and cash equivalents at end of period | 28,066 | 35,997 | 39,566 |
Supplemental information: | |||
Interest paid, net of amounts capitalized | 67,440 | 66,623 | 65,552 |
Income taxes paid (received) | $ (19,032) | $ 43,225 | $ 24,247 |
Consolidated Statements of Equi
Consolidated Statements of Equity and Redeemable Noncontrolling Interest - USD ($) $ in Thousands | Total | Common Stock [Member] | Additional Paid-in Capital [Member] | Accumulated Other Comprehensive Income (Loss) [Member] | Retained Earnings [Member] | Non-controlling Interest [Member] | Redeemable Noncontrolling Interest (Temporary Equity) [Member] | |
Balance at Dec. 31, 2013 | $ 1,412,395 | $ 47,986 | $ 840,521 | $ (41,698) | $ 567,714 | $ (2,128) | ||
Balance, Shares at Dec. 31, 2013 | 46,356,000 | |||||||
Common stock issuances, Value | 11,027 | $ 167 | 10,860 | |||||
Common stock issuances, Shares | 167,000 | |||||||
Redeemable noncontrolling interest attributable to acquisition | $ 18,952 | |||||||
Net income (loss) | 140,997 | 141,126 | (129) | |||||
Net income (loss) attributable to temporary equity | 151 | |||||||
Redemption value adjustments (Note 16) | (961) | (961) | ||||||
Redemption value adjustments attributable to temporary equity | 961 | |||||||
Foreign currency exchange translation adj. | (637) | (637) | ||||||
Foreign currency exchange translation adj attributable to temporary equity | (22) | |||||||
Net actuarial gain (loss) arising during the period, less amortization of unamortized benefit plan cost, net of tax (Notes 5 and 10) | (9,913) | (9,913) | ||||||
Amounts reclassified into net income (Notes 5 and 13) | 2,073 | 2,073 | ||||||
Dividends declared Common | (68,715) | (68,715) | ||||||
Balance at Dec. 31, 2014 | 1,486,266 | $ 48,153 | 851,381 | (50,175) | 639,164 | (2,257) | ||
Balance, Shares at Dec. 31, 2014 | 46,523,000 | |||||||
Balance, Attributable to temporary equity | 20,042 | |||||||
Common stock issuances, Value | 40,144 | $ 854 | 39,290 | |||||
Common stock issuances, Shares | 854,000 | |||||||
Net income (loss) | 138,491 | 138,317 | 174 | |||||
Net income (loss) attributable to temporary equity | 939 | |||||||
Redemption value adjustments (Note 16) | 4,708 | 5,777 | (1,069) | |||||
Redemption value adjustments attributable to temporary equity | (4,708) | |||||||
Foreign currency exchange translation adj. | (1,888) | (1,888) | ||||||
Foreign currency exchange translation adj attributable to temporary equity | (66) | |||||||
Net actuarial gain (loss) arising during the period, less amortization of unamortized benefit plan cost, net of tax (Notes 5 and 10) | (278) | (278) | ||||||
Amounts reclassified into net income (Notes 5 and 13) | 2,073 | 2,073 | ||||||
Centuri distribution to redeemable noncontrolling interest | (99) | |||||||
Dividends declared Common | (77,191) | (77,191) | ||||||
Balance at Dec. 31, 2015 | $ 1,592,325 | $ 49,007 | 896,448 | (50,268) | 699,221 | (2,083) | ||
Balance, Shares at Dec. 31, 2015 | 47,377,575 | 47,377,000 | ||||||
Balance, Attributable to temporary equity | $ 16,108 | 16,108 | ||||||
Common stock issuances, Value | 6,780 | $ 105 | 6,675 | |||||
Common stock issuances, Shares | 105,000 | |||||||
Net income (loss) | 151,907 | 152,041 | (134) | |||||
Net income (loss) attributable to temporary equity | 1,148 | |||||||
Redemption value adjustments (Note 16) | (5,768) | 0 | (5,768) | |||||
Redemption value adjustments attributable to temporary equity | 5,768 | |||||||
Foreign currency exchange translation adj. | 156 | 156 | ||||||
Foreign currency exchange translation adj attributable to temporary equity | 5 | |||||||
Net actuarial gain (loss) arising during the period, less amortization of unamortized benefit plan cost, net of tax (Notes 5 and 10) | 29 | 29 | ||||||
Amounts reclassified into net income (Notes 5 and 13) | 2,075 | 2,075 | ||||||
Centuri distribution to redeemable noncontrolling interest | (439) | |||||||
Dividends declared Common | (86,231) | (86,231) | ||||||
Balance at Dec. 31, 2016 | $ 1,661,273 | $ 49,112 | $ 903,123 | $ (48,008) | $ 759,263 | $ (2,217) | ||
Balance, Shares at Dec. 31, 2016 | 47,482,068 | 47,482,000 | [1] | |||||
Balance, Attributable to temporary equity | $ 22,590 | $ 22,590 | ||||||
[1] | There are 3.8 million common shares registered and available for issuance under provisions of the various stock issuance plans. |
Consolidated Statements of Equ8
Consolidated Statements of Equity and Redeemable Noncontrolling Interest (Parenthetical) - $ / shares | 12 Months Ended | ||
Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2014 | |
Statement of Stockholders' Equity [Abstract] | |||
Dividends declared Common, per share | $ 1.80 | $ 1.62 | $ 1.46 |
Shares registered and available for issuance | 3,800,000 |
Summary of Significant Accounti
Summary of Significant Accounting Policies | 12 Months Ended |
Dec. 31, 2016 | |
Accounting Policies [Abstract] | |
Summary of Significant Accounting Policies | Note 1 — Summary of Significant Accounting Policies Holding Company Reorganization. one-for-one Nature of Operations. Acquisition of Construction Services Businesses Basis of Presentation. Consolidation. Centuri, through its subsidiaries, holds a 65% interest in a venture to market natural gas engine-driven heating, ventilating, and air conditioning (“HVAC”) technology and products. Centuri consolidates the entity (IntelliChoice Energy, LLC). Centuri, through its subsidiaries, holds a 50% interest in W.S. Nicholls Western Construction LTD. (“Western”), a Canadian construction services company that is a variable interest entity. Centuri determined that it is not the primary beneficiary of the entity due to a shared-power structure; therefore, Centuri does not consolidate the entity and has recorded its investment, and results related thereto, using the equity method. The investment in Western totaled $10.8 million at December 31, 2015 and 2016. Both periods include the impacts of foreign currency exchange translation adjustments. Dividends of $500,000 were received from Western during 2016 with no impact on earnings. No dividends were received from Western in 2015. A management fee was paid by Western to its partners, including W.S. Nicholls, in accordance with underlying agreements. The equity method investment in Western is included in Other Property and Investments in the Consolidated Balance Sheets. Centuri’s maximum exposure to loss as a result of its involvement with Western is estimated at $35.8 million. The estimated maximum exposure to loss represents the maximum loss that would be absorbed by Centuri in the event that all of the assets of Western were deemed to be worthless. Centuri recorded earnings of $69,000 from this investment in 2016, which is included in Other Income (deductions) in the Consolidated Statements of Income. In addition, Centuri, through its subsidiaries, has a 25% interest in CCI-TBN Net Utility Plant. Other Property and Investments. 2016 2015 Centuri property, equipment, and intangibles $ 451,114 $ 423,369 Centuri accumulated provision for depreciation and amortization (228,374 ) (221,028 ) Net cash surrender value of COLI policies 106,744 99,276 Other property 12,859 11,914 Total $ 342,343 $ 313,531 Deferred Purchased Gas Costs. Prepaids and other current assets Income Taxes. Cash and Cash Equivalents. Significant non-cash non-cash non-cash non-cash Goodwill. th Natural Construction Consolidated (In thousands of dollars) December 31, 2015 $ 10,095 $ 116,050 $ 126,145 Additional goodwill from ETTI acquisition — 10,726 10,726 Foreign currency translation adjustment — 3,112 3,112 December 31, 2016 $ 10,095 $ 129,888 $ 139,983 Goodwill from the ETTI acquisition consists of the excess of purchase price over the fair value of the acquired net assets and represents the value of the assembled workforce and the estimated economic value attributable to future opportunities that will arise based on the strong financial performance of the combined entities. Acquisition of Construction Services Businesses. Assets acquired in the transaction were recorded at their acquisition date fair values. The final purchase accounting is complete. The final estimated fair values of assets acquired as of May 6, 2016, the acquisition date, are as follows (in millions of dollars): Acquisition Property, plant and equipment $ 4.3 Intangible assets 2.9 Goodwill 10.7 Total assets acquired $ 17.9 The purchase price consisted of $17 million in cash on the acquisition date with the remaining amount being deferred over four years. Intangible Assets December 31, 2016 Gross Carrying Accumulated Net Carrying Customer relationships $ 34,033 $ (3,906 ) $ 30,127 Trade names and trademarks 9,349 (2,565 ) 6,784 Customer contracts backlog 1,656 (1,656 ) — Noncompete agreement 1,029 (271 ) 758 Total $ 46,067 $ (8,398 ) $ 37,669 December 31, 2015 Customer relationships $ 31,226 $ (2,070 ) $ 29,156 Trade names and trademarks 8,621 (1,331 ) 7,290 Customer contracts backlog 1,606 (1,606 ) — Noncompete agreement 437 (110 ) 327 Total $ 41,890 $ (5,117 ) $ 36,773 The intangible assets (other than goodwill and software-related intangibles) are included in Other property and investments in the Consolidated Balance Sheets. The estimated future amortization of the intangible assets for the next five years is as follows (in thousands): 2017 $ 3,339 2018 3,126 2019 2,463 2020 2,395 2021 2,269 See Note 2 – Utility Plant and Leases for additional information regarding natural gas operations intangible assets. Accumulated Removal Costs. Gas Operating Revenues. The Company acts as an agent for state and local taxing authorities in the collection and remission of a variety of taxes, including sales and use taxes and surcharges. These taxes are not included in gas operating revenues. Management uses the net classification method to report taxes collected from customers to be remitted to governmental authorities. Construction Revenues. percentage-of-completion Construction Expenses. job-related Net Cost of Gas Sold. Operations and Maintenance Expense. Depreciation and Amortization. Accumulated Removal Costs Allowance for Funds Used During Construction (“AFUDC”). 2016 2015 2014 (In thousands) AFUDC: Debt portion $ 1,175 $ 1,666 $ 1,228 Equity portion 2,289 3,008 1,995 AFUDC capitalized as part of utility plant $ 3,464 $ 4,674 $ 3,223 AFUDC rate 7.35 % 7.32 % 7.73 % Other Income (Deductions). 2016 2015 2014 Change in COLI policies $ 7,400 $ (500 ) $ 5,300 Interest income 1,849 2,173 2,602 Equity AFUDC 2,289 3,008 1,995 Foreign currency transaction gain (loss) (22 ) (824 ) (178 ) Equity in earnings of unconsolidated investment - Western 69 310 107 Miscellaneous income and (expense) (2,116 ) (1,288 ) (2,719 ) Total other income (deductions) $ 9,469 $ 2,879 $ 7,107 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 the Company 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 Foreign Currency Translation. Earnings Per Share. 2016 2015 2014 (In thousands) Average basic shares 47,469 46,992 46,494 Effect of dilutive securities: Stock options 1 8 17 Performance shares 124 171 215 Restricted stock units 220 212 218 Average diluted shares 47,814 47,383 46,944 Recently Issued Accounting Standards Updates. one-year Management has substantially completed the evaluation of the sources of revenue and are currently assessing the effect of the new guidance on the financial position, results of operations and cash flows. The assessment is contingent, in part, upon the completion of deliberations currently in progress by the utility industry, notably in connection with efforts to produce an accounting guide intended to be developed by the American Institute of Certified Public Accountants (“AICPA”). In association with this undertaking, the AICPA formed a number of industry task forces, including a Power & Utilities (“P&U”) Task Force, on which Company personnel actively participate via formal membership. Industry representatives and organizations, the largest auditing firms, the AICPA’s Revenue Recognition Working Group and its Financial Reporting Executive Committee have undertaken, and continue to undertake, consideration of several items relevant to the utility industry. Where applicable or necessary, the FASB’s Transition Resource Group (TRG) is also participating. Currently, the industry is working to address several items including the evaluation of collectability from customers if a utility has regulatory mechanisms to help assure recovery of uncollected accounts from ratepayers and the accounting for funds received from third parties to partially or fully reimburse the cost of construction of an asset. Currently, a timeline for the resolution of these deliberations has not been established. Southwest is actively working with its peers in the rate-regulated natural gas industry and with the public accounting profession to conclude on the accounting treatment for several other issues that are not expected to be addressed by the P&U Task Force. As of December 31, 2016, the construction services segment has substantially completed the evaluation of sources of revenue and is currently assessing the effect of the new guidance on financial position, results of operations and cash flows. The principals of the new revenue recognition guidance are very similar to existing guidance for construction contractors. Similar to the P&U Task Force noted above, the AICPA formed the Engineering and Construction Contractors Task Force to assist the construction industry with implementing the new guidance. The accounting guide the AICPA intends to release is expected to provide implementation guidance related to several issues including 1) combining contracts and separating performance obligations; 2) estimating change orders, incentives, penalties, liquidated damages and other variable consideration items and 3) acceptable measures of progress when recognizing revenue over time. Given the uncertainty with respect to the conclusions that might arise from the deliberations on issues associated with both the natural gas and construction services segments, the Company is currently unable to determine the effect the new guidance will have on its financial position, results of operations, cash flows, business processes, or the transition method it will utilize to adopt the new guidance. In January 2016, the FASB issued the update “Financial Instruments – Overall (Subtopic 825-10): In February 2016, the FASB issued the update “Leases (Topic 842)”. Under the update, lessees will be required to recognize the following for all leases (with the exception of short-term leases) at the commencement date: • A lease liability, which is a lessee’s obligation to make lease payments arising from a lease, measured on a discounted basis; and • A right-of-use Under the new guidance, lessor accounting is largely unchanged. Certain targeted improvements were made to align, where necessary, lessor accounting with the lessee accounting model and Topic 606, Revenue from Contracts with Customers. Though companies have historically been required to make disclosures regarding leases and of contractual obligations, leases (with terms longer than a year) will no longer exist off-balance In March 2016, the FASB issued the update “Compensation – Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting”. The amendments are intended to improve the accounting for employee share-based payments and affect all organizations that issue share-based payment awards to their employees. The update requires the recording of all of the tax effects related to share-based payments at settlement (or expiration) through the income statement. Currently, tax benefits in excess of compensation cost (“windfalls”) are recorded in equity, and tax deficiencies (“shortfalls”) are recorded in equity to the extent of previous windfalls, and then recorded in the income statement. While the simplification will reduce some of the administrative complexities by eliminating the need to track a “windfall pool,” it will increase the volatility of income tax expense. The update also allows entities to withhold shares for the employee tax burden up to the employees’ maximum individual tax rate in the relevant jurisdiction without resulting in a liability classification of the award (currently such withholding is limited to the employer’s minimum statutory withholding). The update clarifies that all cash payments made to taxing authorities on the employees’ behalf for withheld shares should be presented as financing activities on the statement of cash flows. Also, the update requires all tax-related In June 2016, the FASB issued the update “Financial Instruments – Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments”. The update amends guidance on reporting credit losses for financial assets held at amortized cost basis and available for sale debt securities. For assets held at amortized cost basis, the update eliminates the “probable” threshold for initial recognition of credit losses in current U.S. GAAP and, instead, requires an entity to reflect its current estimate of all expected credit losses. The allowance for credit losses is a valuation account that is deducted from the amortized cost basis of the financial asset to present the net amount expected to be collected. For available for sale debt securities, credit losses should be measured in a manner similar to current U.S. GAAP, however the update will require that credit losses be presented as an allowance rather than as a write-down. This update affects entities holding financial assets and net investment in leases that are not accounted for at fair value through net income. The update affects loans, debt securities, trade receivables, net investments in leases, off-balance In August 2016, the FASB issued the update “Classification of Certain Cash Receipts and Cash Payments”. This update addresses the following specific cash flow issues: debt prepayment or debt extinguishment costs; settlement of zero-coupon In October 2016, the FASB issued the update “Accounting for Income Taxes: Intra-Entity Asset Transfers of Assets Other than Inventory.” This update eliminates the current U.S. GAAP exception for all intra-entity sales of assets other than inventory. As a result, a reporting entity would recognize the tax expense from the sale of the asset in the seller’s tax jurisdiction when the transfer occurs, even though the pre-tax In October 2016, the FASB issued the update “Consolidation (Topic 810): Interests Held through Related Parties That Are under Common Control.” The amendments affect reporting entities that are required to evaluate whether they should consolidate a variable interest entity in certain situations involving entities under common control. The update is effective for fiscal and interim periods beginning after December 15, 2016. Management has determined that this update is not impactful to its consolidated financial statements. In January 2017, the FASB issued the update “Intangibles – Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment.” The update eliminates Step 2 from the goodwill impairment test. The annual, or interim, goodwill impairment test is performed by comparing the fair value of a reporting unit with its carrying amount. An impairment charge should be recognized for the amount by which the carrying amount exceeds the reporting unit’s fair value; however, the loss recognized should not exceed the total amount of goodwill allocated to that reporting unit. In addition, income tax effects from any tax deductible goodwill on the carrying amount of the reporting unit should be considered when measuring the goodwill impairment loss, if applicable. The update also eliminates the requirements for any reporting unit with a zero or negative carrying amount to perform a qualitative assessment and, if it fails that qualitative test, to perform Step 2 of the goodwill impairment test. An entity still has the option to perform the qualitative assessment for a reporting unit to determine if the quantitative impairment test is necessary. The amendments should be applied on a prospective basis. The update is effective for fiscal and interim periods beginning after December 15, 2019. Early adoption is permitted for interim or annual goodwill impairment tests performed on testing dates after January 1, 2017. Management has determined that this update would have had no impact on the consolidated financial statements for the periods presented if it had been effective during those periods. Subsequent Events. |
Utility Plant and Leases
Utility Plant and Leases | 12 Months Ended |
Dec. 31, 2016 | |
Leases [Abstract] | |
Utility Plant and Leases | Note 2 – Utility Plant and Leases Net utility plant as of December 31, 2016 and 2015 was as follows (thousands of dollars): December 31, 2016 2015 Gas plant: Storage $ 24,614 $ 22,944 Transmission 349,981 312,996 Distribution 5,198,531 4,935,730 General 382,084 365,865 Software and software-related intangibles 224,260 203,323 Other 14,094 14,059 6,193,564 5,854,917 Less: accumulated depreciation (2,172,966 ) (2,084,007 ) Acquisition adjustments, net 196 370 Construction work in progress 111,177 119,805 Net utility plant $ 4,131,971 $ 3,891,085 Utility plant depreciation is computed on the straight-line remaining life method at composite rates considered sufficient to amortize costs over estimated service lives, including components which compensate for removal costs (net of salvage value), and retirements, based on the processes of regulatory proceedings and related regulatory commission approvals and/or mandates. In 2016, annual depreciation and amortization expense averaged 3.6% of the original cost of depreciable and amortizable property. Average rates in 2015 and 2014 also approximated 3.6%. Transmission and Distribution plant (combined), associated with our core natural gas delivery infrastructure, constitute the majority of gas plant. Annual depreciation expense averaged approximately 3.3% of original cost of depreciable transmission and distribution plant during the period 2014 through 2016. Depreciation and amortization expense on gas plant, including intangibles, was as follows (thousands of dollars): 2016 2015 2014 Depreciation and amortization expense $ 214,037 $ 201,233 $ 194,360 Included in the figures above is amortization of intangibles of $14.8 million in 2016, $12.7 million in 2015, and $11.7 million in 2014. Operating Leases and Rentals. 2016 2015 2014 Southwest Gas $ 4,357 $ 4,186 $ 5,330 Centuri 53,956 45,849 30,012 Consolidated rental payments/lease expense $ 58,313 $ 50,035 $ 35,342 The following is a schedule of future minimum lease payments for significant non-cancelable Year Ending December 31, 2017 $ 6,929 2018 4,837 2019 3,449 2020 2,411 2021 1,098 Thereafter 2,730 Total minimum lease payments $ 21,454 Capital Leases. December 31, 2016 2015 Capital leased assets, gross $ 3,189 $ 4,584 Less: accumulated amortization (1,172 ) (1,043 ) Capital leased assets, net $ 2,017 $ 3,541 The following is a schedule of future minimum lease payments for non-cancelable Year Ending December 31, 2017 $ 931 2018 546 2019 84 2020 — 2021 — Thereafter — 1,561 Less: amount representing interest (101 ) Total minimum lease payments $ 1,460 |
Receivables and Related Allowan
Receivables and Related Allowances | 12 Months Ended |
Dec. 31, 2016 | |
Receivables [Abstract] | |
Receivables and Related Allowances | Note 3 – Receivables and Related Allowances Business activity with respect to gas utility operations is conducted with customers located within the three-state region of Arizona, Nevada, and California. The table below contains information about the gas utility customer accounts receivable balance (net of allowance) at December 31, 2016 and 2015, and the percentage of customers in each of the three states. December 31, December 31, Gas utility customer accounts receivable balance (in thousands) $ 111,320 $ 151,775 December 31, Percent of customers by state Arizona 53 % Nevada 37 % California 10 % Although Southwest seeks to minimize its credit risk related to utility operations by requiring security deposits from new customers, imposing late fees, and actively pursuing collection on overdue accounts, some accounts are ultimately not collected. Customer accounts are subject to collection procedures that vary by jurisdiction (late fee assessment, noticing requirements for disconnection of service, and procedures for actual disconnection and/or reestablishment of service). After disconnection of service, accounts are generally written off approximately one month after inactivation. Dependent upon the jurisdiction, reestablishment of service requires both payment of previously unpaid balances and additional deposit requirements. Provisions for uncollectible accounts are recorded monthly based on experience, customer and rate composition, and write-off Allowance for Balance, December 31, 2013 $ 1,725 Additions charged to expense 4,146 Accounts written off, less recoveries (3,616 ) Balance, December 31, 2014 2,255 Additions charged to expense 4,113 Accounts written off, less recoveries (4,098 ) Balance, December 31, 2015 2,270 Additions charged to expense 3,264 Accounts written off, less recoveries (3,010 ) Balance, December 31, 2016 $ 2,524 At December 31, 2016, the construction services segment (Centuri) had $173 million in customer accounts receivable. Both the allowance for uncollectibles and write-offs related to Centuri customers have been insignificant and are not reflected in the table above. |
Regulatory Assets and Liabiliti
Regulatory Assets and Liabilities | 12 Months Ended |
Dec. 31, 2016 | |
Regulated Operations [Abstract] | |
Regulatory Assets and Liabilities | Note 4 – Regulatory Assets and Liabilities Southwest is subject to the regulation of the Arizona Corporation Commission (“ACC”), the Public Utilities Commission of Nevada (“PUCN”), the California Public Utilities Commission (“CPUC”), and the Federal Energy Regulatory Commission (“FERC”). Accounting policies of Southwest conform to U.S. GAAP applicable to rate-regulated entities and reflect the effects of the ratemaking process. Accounting treatment for rate-regulated entities allows for deferral as regulatory assets, costs that otherwise would be expensed, if it is probable that future recovery from customers will occur. If rate recovery is no longer probable, due to competition or the actions of regulators, Southwest is required to write-off The following table represents existing regulatory assets and liabilities (thousands of dollars): December 31, 2016 2015 Regulatory assets: Accrued pension and other postretirement benefit costs (1) $ 379,063 $ 384,647 Unrealized net loss on non-trading — 5,486 Deferred purchased gas costs (3) 2,608 3,591 Accrued purchased gas costs (4) 37,100 — Unamortized premium on reacquired debt (5) 21,975 21,511 Accrued absence time (9) 13,440 13,240 Other (6) 23,557 59,782 477,743 488,257 Regulatory liabilities: Deferred purchased gas costs (3) (90,476 ) (45,601 ) Accumulated removal costs (308,000 ) (303,000 ) Accrued purchased gas costs (4) — (10,400 ) Unrealized net gain on non-trading (4,377 ) — Unamortized gain on reacquired debt (7) (9,789 ) (10,325 ) Other (8) (24,659 ) (36,631 ) Net regulatory assets $ 40,442 $ 82,300 (1) Included in Deferred charges and other assets on the Consolidated Balance Sheets. Recovery period is greater than five years. (See Note 10). (2) The following table details the regulatory assets/(liabilities) offsetting the derivatives (Swaps) at fair value in the Consolidated Balance Sheets (thousands of dollars). The actual amounts, when realized at settlement, become a component of purchased gas costs under Southwest’s purchased gas adjustment (“PGA”) mechanisms. (See Note 13). Instrument Balance Sheet Location 2016 2015 Swaps Deferred charges and other assets $ — $ 1,219 Swaps Prepaids and other current assets — 4,267 Swaps Other current liabilities (3,532 ) — Swaps Other deferred credits (845 ) — (3) Balance recovered or refunded on an ongoing basis with interest. (4) Asset included in Prepaids and other current assets and liability included in Other current liabilities on the Consolidated Balance Sheets. Balance recovered or refunded on an ongoing basis. (5) Included in Deferred charges and other assets on the Consolidated Balance Sheets. Recovered over life of debt instruments. (6) The following table details the components of Other regulatory assets which are included in either Prepaids and other current assets or Deferred charges and other assets on the Consolidated Balance Sheets (as indicated). Recovery periods vary. Margin tracking/decoupling mechanisms are alternative revenue programs and revenue associated with under-collections (for the difference between authorized margin levels and amounts billed to customers through rates currently) are recognized as revenue so long as recovery is expected to take place within 24 months. Other Regulatory Assets 2016 2015 State mandated public purpose programs (including low income and conservation programs) (a) (f) $ 7,096 $ 18,101 Margin and interest-tracking accounts (b) (f) 3,517 30,339 Infrastructure replacement programs and similar (c) (f) 6,976 6,947 Environmental compliance programs (d) (f) 4,329 2,300 Other (e) 1,639 2,095 $ 23,557 $ 59,782 a) 2016 included in Prepaids and other current assets on the Consolidated Balance Sheets; 2015 included in Deferred charges and other assets on the Consolidated Balance Sheets. b) 2016 included in Prepaids and other current assets on the Consolidated Balance Sheets; 2015 included in Prepaids and other current assets on the Consolidated Balance Sheets ($11 million) and Deferred charges and other assets on the Consolidated Balance Sheets ($19.3 million). c) Included in Deferred charges and other assets on the Consolidated Balance Sheets with the exception of $6,000 in 2016 that is included in Prepaids and other current assets on the Consolidated Balance Sheets. d) 2016 included in Prepaids and other current assets on the Consolidated Balance Sheets ($3.8 million) and Deferred charges and other assets on the Consolidated Balance Sheets ($500,000); 2015 included in Prepaids and other current assets on the Consolidated Balance Sheets ($1.8 million) and Deferred charges and other assets on the Consolidated Balance Sheets ($484,000). e) 2016 included in Prepaids and other current assets on the Consolidated Balance Sheets ($622,000) and Deferred charges and other assets on the Consolidated Balance Sheets ($1 million); 2015 included in Deferred charges and other assets on the Consolidated Balance Sheets. f) Balance recovered or refunded on an ongoing basis, generally with interest. (7) Included in Other deferred credits on the Consolidated Balance Sheets. Amortized over life of debt instruments. (8) The following table details the components of Other regulatory liabilities which are included in either Other current liabilities or Deferred credits and other liabilities on the Consolidated Balance Sheets (as indicated). Other Regulatory Liabilities 2016 2015 State mandated public purpose programs (including low income and conservation programs) (a) (d) $ (7,101 ) $ (4,888 ) Margin and interest-tracking accounts (a) (d) (3,668 ) (20,191 ) Environmental compliance programs (b) (d) (4,469 ) (2,252 ) Regulatory offsets to deferred tax balances (c) (3,390 ) (4,866 ) Regulatory accounts for differences related to pension funding (c) (2,284 ) (1,363 ) Income tax and gross-up (c) (3,203 ) (3,067 ) Other (d) (e) (544 ) (4 ) $ (24,659 ) $ (36,631 ) a) 2016 included in Other current liabilities on the Consolidated Balance Sheets; 2015 included in Other deferred credits and other long-term liabilities on the Consolidated Balance Sheets. b) Included in Other current liabilities on the Consolidated Balance Sheets. c) Included in Other deferred credits and other long-term liabilities on the Consolidated Balance Sheets. d) Balance recovered or refunded on an ongoing basis, generally with interest. e) 2016 included in Other current liabilities on the Consolidated Balance Sheets ($536,000) and in Other deferred credits and other long-term liabilities on the Consolidated Balance Sheets ($8,000); 2015 included in Other deferred credits and other long-term liabilities on the Consolidated Balance Sheets. (9) Regulatory recovery occurs on a one-year |
Other Comprehensive Income and
Other Comprehensive Income and Accumulated Other Comprehensive Income ("AOCI") | 12 Months Ended |
Dec. 31, 2016 | |
Equity [Abstract] | |
Other Comprehensive Income and Accumulated Other Comprehensive Income ("AOCI") | Note 5 – Other Comprehensive Income and Accumulated Other Comprehensive Income (“AOCI”) The following information provides insight into amounts impacting Other Comprehensive Income (Loss), both before and after-tax, Related Tax Effects Allocated to Each Component of Other Comprehensive Income (Loss) (Thousands of dollars) 2016 2015 2014 Before- Tax Amount Tax (Expense) or Net-of- Tax Amount Before- Tax Amount Tax (Expense) or Benefit (1) Net-of- Tax Amount Before- Tax Amount Tax (Expense) or Benefit (1) Net-of- Tax Amount Defined benefit pension plans: Net actuarial gain/(loss) $ (22,770 ) $ 8,652 $ (14,118 ) $ (30,519 ) $ 11,597 $ (18,922 ) $ (173,646 ) $ 65,985 $ (107,661 ) Amortization of prior service cost 1,335 (507 ) 828 1,335 (507 ) 828 355 (135 ) 220 Amortization of net actuarial (gain)/loss 27,066 (10,285 ) 16,781 34,381 (13,065 ) 21,316 23,656 (8,989 ) 14,667 Prior service cost — — — — — — (6,661 ) 2,531 (4,130 ) Regulatory adjustment (5,584 ) 2,122 (3,462 ) (5,646 ) 2,146 (3,500 ) 140,308 (53,317 ) 86,991 Pension plans other comprehensive income (loss) 47 (18 ) 29 (449 ) 171 (278 ) (15,988 ) 6,075 (9,913 ) Forward-starting interest rate swaps (“FSIRS”) (designated hedging activities): Amounts reclassified into net income 3,345 (1,270 ) 2,075 3,344 (1,271 ) 2,073 3,345 (1,272 ) 2,073 FSIRS other comprehensive income (loss) 3,345 (1,270 ) 2,075 3,344 (1,271 ) 2,073 3,345 (1,272 ) 2,073 Foreign currency translation adjustments: Translation adjustments 161 — 161 (1,954 ) — (1,954 ) (659 ) — (659 ) Foreign currency other comprehensive income (loss) 161 — 161 (1,954 ) — (1,954 ) (659 ) — (659 ) Total other comprehensive income (loss) $ 3,553 $ (1,288 ) $ 2,265 $ 941 $ (1,100 ) $ (159 ) $ (13,302 ) $ 4,803 $ (8,499 ) (1) Tax amounts are calculated using a 38% rate. Management has elected to indefinitely reinvest the earnings of Centuri’s Canadian subsidiaries in Canada, thus preventing deferred taxes on such earnings. As a result of this assertion, management is not recognizing any tax effect or presenting a tax expense or benefit for the currency translation adjustment amount reported in Other Comprehensive Income, as repatriation of earnings is not anticipated. The estimated amounts that will be amortized from accumulated other comprehensive income or regulatory assets into net periodic benefit cost over the next year are summarized below (in thousands): Retirement plan net actuarial loss $ 24,000 SERP net actuarial loss 1,500 PBOP prior service cost 1,300 Approximately $2.1 million of realized losses (net of tax) related to the FSIRS, included in AOCI at December 31, 2016, will be reclassified into interest expense within the next twelve months as the related interest payments on long-term debt occur. The following table represents a rollforward of AOCI, presented on the Company’s Consolidated Balance Sheets and its Consolidated Statements of Equity: AOCI—Rollforward (Thousands of dollars) Defined Benefit Plans (Note 10) FSIRS (Note 13) Foreign Currency Items Before- Tax Tax After- Tax Before- Tax Tax After- Tax Before- Tax Tax After- Tax AOCI Beginning Balance AOCI December 31, 2015 $ (57,660 ) $ 21,911 $ (35,749 ) $ (19,344 ) $ 7,350 $ (11,994 ) $ (2,525 ) $ — $ (2,525 ) $ (50,268 ) Net actuarial gain/(loss) (22,770 ) 8,652 (14,118 ) — — — — — — (14,118 ) Translation adjustments — — — — — — 161 — 161 161 Other comprehensive income before reclassifications (22,770 ) 8,652 (14,118 ) — — — 161 — 161 (13,957 ) FSIRS amounts reclassified from AOCI (1) — — — 3,345 (1,270 ) 2,075 — — — 2,075 Amortization of prior service cost (2) 1,335 (507 ) 828 — — — — — — 828 Amortization of net actuarial loss (2) 27,066 (10,285 ) 16,781 — — — — — — 16,781 Regulatory adjustment (3) (5,584 ) 2,122 (3,462 ) — — — — — — (3,462 ) Net current period other comprehensive income (loss) 47 (18 ) 29 3,345 (1,270 ) 2,075 161 — 161 2,265 Less: Translation adjustment attributable to redeemable noncontrolling interest — — — — — — 5 — 5 5 Net current period other comprehensive income (loss) attributable to Southwest Gas Corporation 47 (18 ) 29 3,345 (1,270 ) 2,075 156 — 156 2,260 Ending Balance AOCI December 31, 2016 $ (57,613 ) $ 21,893 $ (35,720 ) $ (15,999 ) $ 6,080 $ (9,919 ) $ (2,369 ) $ — $ (2,369 ) $ (48,008 ) (1) The FSIRS reclassification amounts are included in the Net interest deductions line item on the Consolidated Statements of Income. (2) These AOCI components are included in the computation of net periodic benefit cost (see Note 10 – Pension and Other Postretirement Benefits (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 Consolidated Balance Sheets). (4) Tax amounts are calculated using a 38% rate. The following table represents amounts (before income tax impacts) included in Accumulated other comprehensive income (in the table above), that have not yet been recognized in net periodic benefit cost as of December 31, 2016 and 2015: Amounts Recognized in AOCI (Before Tax) (Thousands of dollars) 2016 2015 Net actuarial (loss) gain $ (430,973 ) $ (435,269 ) Prior service cost (5,703 ) (7,038 ) Less: amount recognized in regulatory assets 379,063 384,647 Recognized in AOCI $ (57,613 ) $ (57,660 ) See Note 10 – Pension and Other Postretirement Benefits for more information on the defined benefit pension plans and Note 13 – Derivatives and Fair Value Measurements for more information on the FSIRS. |
Common Stock
Common Stock | 12 Months Ended |
Dec. 31, 2016 | |
Text Block [Abstract] | |
Common Stock | Note 6 – Common Stock On March 10, 2015, the Company filed with the Securities Exchange Commission (“SEC”) an automatic shelf registration statement on Form S-3 No. 333-202633), at-the-market During 2016, the Company issued approximately 105,000 shares of common stock through the Stock Incentive Plan, Restricted Stock/Unit Plan, and Management Incentive Plan. |
Long-Term Debt
Long-Term Debt | 12 Months Ended |
Dec. 31, 2016 | |
Debt Disclosure [Abstract] | |
Long-Term Debt | Note 7 – Long-Term Debt Carrying amounts of the Company’s long-term debt and their related estimated fair values as of December 31, 2016 and December 31, 2015 are disclosed in the following table. The fair values of the revolving credit facility (including commercial paper) and the variable-rate Industrial Development Revenue Bonds (“IDRBs”) approximate their carrying values, as they are repaid quickly (in the case of credit facility borrowings) and have interest rates that reset frequently. They are categorized as Level 1 (quoted prices for identical financial instruments) within the three-level December 31, 2016 2015 Carrying Amount Market Value Carrying Amount Market Value (Thousands of dollars) Debentures: Notes, 4.45%, due 2020 $ 125,000 $ 129,703 $ 125,000 $ 130,273 Notes, 6.1%, due 2041 125,000 149,734 125,000 141,581 Notes, 3.875%, due 2022 250,000 254,900 250,000 253,600 Notes, 4.875%, due 2043 250,000 266,793 250,000 251,483 Notes, 3.8%, due 2046 300,000 283,029 — — 8% Series, due 2026 75,000 94,691 75,000 97,035 Medium-term notes, 7.59% series, due 2017 25,000 25,040 25,000 26,253 Medium-term notes, 7.78% series, due 2022 25,000 29,290 25,000 29,855 Medium-term notes, 7.92% series, due 2027 25,000 31,905 25,000 31,890 Medium-term notes, 6.76% series, due 2027 7,500 8,769 7,500 8,684 Unamortized discount and debt issuance costs (9,931 ) (6,137 ) 1,197,569 901,363 Revolving credit facility and commercial paper 5,000 5,000 150,000 150,000 Industrial development revenue bonds: Variable-rate bonds: Tax-exempt 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: 4.85% 2005 Series A, due 2035 — — 100,000 100,452 4.75% 2006 Series A, due 2036 — — 24,855 25,130 Unamortized discount and debt issuance costs (2,489 ) (3,946 ) 197,511 320,909 Centuri term loan facility 106,700 106,819 112,571 112,665 Unamortized debt issuance costs (516 ) (692 ) 106,184 111,879 Centuri secured revolving credit facility 41,185 41,292 60,627 60,724 Centuri other debt obligations 52,635 52,840 25,901 26,059 1,600,084 1,570,679 Less: current maturities (50,101 ) (19,475 ) Long-term debt, less current maturities $ 1,549,983 $ 1,551,204 In March 2016, the Company amended its $300 million credit and commercial paper facility. The facility was previously scheduled to expire in March 2020, but was extended to March 2021. The Company will continue to use $150 million of the facility as long-term debt and the remaining $150 million for working capital purposes. 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 December 31, 2016, 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. At December 31, 2016, $5 million was outstanding on the long-term portion of the credit facility, none of which was in commercial paper (see commercial paper program discussion below). The effective interest rate on the long-term portion of the credit facility was 5.21% at December 31, 2016. Borrowings under the credit facility ranged from none at various times throughout 2016 to a high of $230 million during the third quarter of 2016. With regard to the short-term portion of the credit facility, there were no borrowings outstanding at December 31, 2016 and $18 million outstanding at December 31, 2015. (See Note 8 – Short-Term Debt ). The Company has a $50 million commercial paper program. Any issuance under the commercial paper program is supported by the Company’s current revolving credit facility and, therefore, does not represent additional borrowing capacity. Any borrowing under the commercial paper program will be designated as long-term debt. Interest rates for the program are calculated at the then current commercial paper rate. At December 31, 2016, and as noted above, no borrowings were outstanding under the commercial paper program. Southwest redeemed its $100 million 2005 4.85% Series A fixed-rate IDRBs (originally due in 2035) at par with accrued interest in July 2016. In September 2016, Southwest redeemed its $24.9 million 2006 Series A 4.75% fixed-rate IDRBs (originally due in 2036) at par with accrued interest. In January 2017, subsequent to the most recent balance sheet date, the $25 million 7.59% medium-term notes were repaid at maturity, using available cash on hand. In September 2016, Southwest issued $300 million in 3.8% Senior Notes at a discount of 0.302%. The notes will mature in September 2046. A portion of the net proceeds were used to temporarily pay down amounts then outstanding under the credit facility. The remaining net proceeds were used for general corporate purposes. Centuri has a $300 million secured revolving credit and term loan facility that is scheduled to expire in October 2019. This facility includes a revolving credit facility and a term loan facility. The term loan facility had an initial limit of approximately $150 million, which was reached in 2014 and is in the process of being repaid. No further borrowing is permitted under the term loan facility. The revolving credit facility has a limit of $150 million; amounts borrowed and repaid under the revolving credit facility are available to be re-borrowed. Interest rates for Centuri’s $300 million secured revolving credit and term loan facility are calculated at the LIBOR, the Canadian Dealer Offered Rate (“CDOR”), or an alternate base rate or Canadian base rate, plus in each case an applicable margin that is determined based on Centuri’s consolidated leverage ratio. The applicable margin ranges from 1.00% to 2.25% for loans bearing interest with reference to LIBOR or CDOR and from 0.00% to 1.25% for loans bearing interest with reference to the alternate base rate or Canadian base rate. Centuri is also required to pay a commitment fee on the unfunded portion of the commitments based on their consolidated leverage ratio. The commitment fee ranges from 0.15% to 0.40% per annum. Borrowings under the revolving credit facility ranged from a low of $36.2 million during February 2016 to a high of $83.2 million during July 2016. All amounts outstanding are considered long-term borrowings. The effective interest rate on the secured revolving credit and term loan facility was 2.63% at December 31, 2016. The effective interest rates on Southwest’s variable-rate IDRBs are included in the table below: December 31, December 31, 2003 Series A 1.47 % 0.87 % 2008 Series A 1.53 % 0.87 % 2009 Series A 1.43 % 0.75 % Tax-exempt 1.51 % 0.81 % In Nevada, interest fluctuations due to changing interest rates on Southwest’s 2003 Series A, 2008 Series A, and 2009 Series A variable-rate IDRBs are tracked and recovered from ratepayers through an interest balancing account. None of Southwest’s debt instruments have credit triggers or other clauses that result in default if bond ratings are lowered by rating agencies. Certain debt instruments contain securities ratings covenants that, if set in motion, would increase financing costs. Certain debt instruments also have leverage ratio caps and minimum net worth requirements. At December 31, 2016, the Company is in compliance with all of its covenants. Under the most restrictive of the covenants, at December 31, 2016, approximately $2.3 billion in additional debt could be issued while still meeting the leverage ratio requirement. Relating to the minimum net worth requirement, as of December 31, 2016, there is at least $1.1 billion of cushion in equity. Certain Centuri debt instruments also have leverage ratio caps and fixed charge ratio coverage requirements. At December 31, 2016, Centuri is in compliance with all of its covenants. Under the most restrictive of the covenants, Centuri could issue approximately $145 million in additional debt and meet the leverage ratio requirement. Centuri has at least $21 million of cushion relating to the minimum fixed charge ratio coverage requirement. Estimated maturities of long-term debt for the next five years are (in thousands): 2017 $ 50,101 2018 24,082 2019 134,534 2020 134,452 2021 7,815 |
Short-Term Debt
Short-Term Debt | 12 Months Ended |
Dec. 31, 2016 | |
Debt Disclosure [Abstract] | |
Short-Term Debt | Note 8 – Short-Term Debt As discussed in Note 7, Southwest has a $300 million credit facility that is scheduled to expire in March 2021, of which $150 million has been designated by management for working capital purposes. Southwest had no short-term borrowings outstanding at December 31, 2016 and $18 million in short-term borrowings outstanding at December 31, 2015. |
Commitments and Contingencies
Commitments and Contingencies | 12 Months Ended |
Dec. 31, 2016 | |
Commitments and Contingencies Disclosure [Abstract] | |
Commitments and Contingencies | Note 9 – Commitments and Contingencies The Company is a defendant in miscellaneous legal proceedings. The Company is also a party to various regulatory proceedings. The ultimate dispositions of these proceedings are not presently determinable; however, it is the opinion of management that no litigation or regulatory proceeding to which the Company is currently subject will have a material adverse impact on its financial position, results of operations, or cash flows. Southwest maintains liability insurance for various risks associated with the operation of its natural gas pipelines and facilities. In connection with these liability insurance policies, Southwest is responsible for an initial deductible or self-insured retention amount per incident, after which the insurance carriers would be responsible for amounts up to the policy limits. For the policy year August 2016 to July 2017, these liability insurance policies require Southwest to be responsible for the first $1 million (self-insured retention) of each incident plus the first $4 million in aggregate claims above its self-insured retention in the policy year. Through an assessment process, Southwest may determine that certain costs are likely to be incurred in the future related to specific legal matters. In these circumstances and in accordance with accounting policies, Southwest will make an accrual, as necessary. |
Pension and Other Postretiremen
Pension and Other Postretirement Benefits | 12 Months Ended |
Dec. 31, 2016 | |
Compensation and Retirement Disclosure [Abstract] | |
Pension and Other Postretirement Benefits | Note 10 – Pension and Other Postretirement Benefits An Employees’ Investment Plan is offered to eligible employees of Southwest through deduction of a percentage of base compensation, subject to IRS limitations. The Employees’ Investment Plan provides for purchases of various mutual fund investments and Company common stock. One-half 2016 2015 2014 Employee Investment Plan cost $ 4,976 $ 5,072 $ 4,816 Centuri has a separate plan, the cost and liability of which are not significant. A deferred compensation plan is offered to all officers and a separate deferred compensation plan for members of the Board of Directors. The plans provide the opportunity to defer up to 100% of annual cash compensation. One-half A noncontributory qualified retirement plan with defined benefits covering substantially all Southwest employees is available in addition to a separate unfunded supplemental executive retirement plan (“SERP”) which is limited to officers. Postretirement benefits other than pensions (“PBOP”) are provided to qualified retirees for health care, dental, and life insurance benefits. The overfunded or underfunded positions of defined benefit postretirement plans, including pension plans, are recognized in the Consolidated Balance Sheets. Any actuarial gains and losses, prior service costs and transition assets or obligations are recognized in Accumulated other comprehensive income under Stockholders’ equity, net of tax, until they are amortized as a component of net periodic benefit cost. A regulatory asset has been established for the portion of the total amounts otherwise chargeable to accumulated other comprehensive income that are expected to be recovered through rates in future periods. Changes in actuarial gains and losses and prior service costs pertaining to the regulatory asset will be recognized as an adjustment to the regulatory asset account as these amounts are amortized and recognized as components of net periodic pension costs each year. Investment objectives and strategies for the qualified retirement plan are developed and approved by the Pension Plan Investment Committee of the Board of Directors of the Company. They are designed to enhance capital, maintain minimum liquidity required for retirement plan operations, manage funded status risk and effectively manage pension assets. A target portfolio of investments in the qualified retirement plan is developed by the Pension Plan Investment Committee and is reevaluated periodically. Asset return assumptions are determined by evaluating performance expectations of the target portfolio. Projected benefit obligations are estimated using actuarial assumptions and Company benefit policy. A target mix of assets is then determined based on acceptable risk versus estimated returns in order to fund the benefit obligation. At December 31, 2016, the percentage ranges of the target portfolio are: Type of Investment Percentage Range Equity securities 63 to 67 Debt securities 33 to 37 Other up to 1 The qualified retirement plan invests the majority of its plan assets in common collective trusts which includes a well-diversified portfolio of domestic and international equity securities and fixed income securities, which are managed by a professional investment manager appointed by the Company. The investment manager has full discretionary authority to direct the investment of plan assets held in trust within the specific guidelines prescribed by the Company through the plan’s investment policy statement. In 2016, the Company adopted a liability driven investment (“LDI”) strategy for part of the portfolio, a form of investing designed to better match the movement in pension plan assets with the impact of interest rate changes and inflation assumption changes on the pension plan liability. The implementation of the LDI strategy will be phased in over time by using a glide path. The glide path is designed to increase the allocation of the plan’s assets to fixed income securities, as the funded status of the plan increases, in order to more closely match the duration of the plan assets to that of the plan liability. During the third quarter of 2016, qualifying term-vested participants were offered a lump-sum one-half In August 2016, Russell Investments Trust Company (“Russell”), an outside professional investment manager as defined in Section 3(38) of ERISA, was engaged as a fiduciary of the pension plan. Russell has full discretionary authority to direct the investment of the pension plan’s assets within the guidelines prescribed by the pension plan’s investment policy statement. The change, related to managing pension plan assets, has no impact on retirement benefit calculations for pension plan participants, and was approved by the Board of Directors of the Company. Pension plan assets are held in a Master Trust. Investment objectives and strategies for the qualified retirement plan are developed and approved by the Pension Plan Investment Committee of the Board of Directors. The objective of the investment policy is to manage assets in such a way that will allow the eventual settlement of the obligations to the pension plan’s beneficiaries. To meet this objective, the pension plan assets are managed by an outside adviser using a portfolio strategy that will provide liquidity to meet the plan’s benefit payment obligations. The pension plan funding policy is in compliance with the federal government’s funding requirements. Pension costs for these plans are affected by the amount and timing of cash contributions to the plans, the return on plan assets, discount rates, and by employee demographics, including age, compensation, and length of service. Changes made to the provisions of the plans may also impact current and future pension costs. Actuarial formulas are used in the determination of pension costs and are affected by actual plan experience and assumptions about future experience. Key actuarial assumptions include the expected return on plan assets, the discount rate used in determining the projected benefit obligation and pension costs, and the assumed rate of increase in employee compensation. Relatively small changes in these assumptions, particularly the discount rate, may significantly affect pension costs and plan obligations for the qualified retirement plan. In determining the discount rate, management matches the plan’s projected cash flows to a spot-rate yield curve based on highly rated corporate bonds. Changes to the discount rate from year-to-year, There was no change in the discount rate between years. The methodology utilized to determine the discount rate was consistent with prior years. The weighted-average rate of compensation increase also remained the same (consistent with management’s expectations overall). The asset return assumption (which impacts the following year’s expense) was lowered. The rates are presented in the table below: December 31, 2016 December 31, 2015 Discount rate 4.50 % 4.50 % Weighted-average rate of compensation increase 3.25 % 3.25 % Asset return assumption 7.00 % 7.25 % Pension expense for 2017 is estimated to be similar to that experienced in 2016. Future years’ expense level movements (up or down) will continue to be greatly influenced by long-term interest rates, asset returns, and funding levels. The following table sets forth the retirement plan, SERP, and PBOP funded statuses and amounts recognized on the Consolidated Balance Sheets and Consolidated Statements of Income. 2016 2015 Qualified Retirement Plan SERP PBOP Qualified Retirement Plan SERP PBOP (Thousands of dollars) Change in benefit obligations Benefit obligation for service rendered to date at beginning of year (PBO/PBO/APBO) $ 1,044,817 $ 42,720 $ 72,632 $ 1,060,240 $ 41,176 $ 72,202 Service cost 22,833 331 1,499 25,123 320 1,641 Interest cost 46,027 1,859 3,180 44,229 1,695 2,999 Actuarial loss (gain) 8,550 1,347 (2,060 ) (44,553 ) 2,322 (3,251 ) Benefits paid (73,874 ) (2,946 ) (1,386 ) (40,222 ) (2,793 ) (959 ) Benefit obligation at end of year (PBO/PBO/APBO) 1,048,353 43,311 73,865 1,044,817 42,720 72,632 Change in plan assets Market value of plan assets at beginning of year 736,880 — 43,584 754,796 — 44,892 Actual return on plan assets 39,956 — 4,818 (13,694 ) — (1,034 ) Employer contributions 36,000 2,946 — 36,000 2,793 — Benefits paid (73,874 ) (2,946 ) (289 ) (40,222 ) (2,793 ) (274 ) Market value of plan assets at end of year 738,962 — 48,113 736,880 — 43,584 Funded status at year end $ (309,391 ) $ (43,311 ) $ (25,752 ) $ (307,937 ) $ (42,720 ) $ (29,048 ) Weighted-average assumptions (benefit obligation) Discount rate 4.50 % 4.50 % 4.50 % 4.50 % 4.50 % 4.50 % Weighted-average rate of compensation increase 3.25 % 3.25 % N/A 3.25 % 3.25 % N/A Estimated funding for the plans above during calendar year 2017 is approximately $39 million, of which $36 million pertains to the retirement plan. Management monitors plan assets and liabilities and could, at its discretion, increase plan funding levels above the minimum in order to achieve a desired funded status and avoid or minimize potential benefit restrictions. The accumulated benefit obligation for the retirement plan and the SERP is presented below (in thousands): December 31, 2016 December 31, 2015 Retirement plan $ 939,002 $ 922,992 SERP 40,852 39,270 Benefits expected to be paid for pension, SERP, and PBOP over the next 10 years are as follows (in millions): 2017 2018 2019 2020 2021 2022-2026 Pension $ 48.6 $ 50.1 $ 51.5 $ 53.2 $ 55.1 $ 294.2 SERP 2.9 2.9 2.9 2.9 2.9 14.4 PBOP 4.1 4.3 4.4 4.5 4.5 20.6 No assurance can be made that actual funding and benefits paid will match these estimates. For PBOP measurement purposes, the per capita cost of the covered health care benefits medical rate trend assumption is 7% declining to 4.5%. Fixed contributions are made for health care benefits of employees who retire after 1988, but Southwest pays all covered health care costs for employees who retired prior to 1989. The medical trend rate assumption noted above applies to the benefit obligations of pre-1989 Components of net periodic benefit cost Qualified Retirement Plan SERP PBOP 2016 2015 2014 2016 2015 2014 2016 2015 2014 (Thousands of dollars) Service cost $ 22,833 $ 25,123 $ 21,360 $ 331 $ 320 $ 292 $ 1,499 $ 1,641 $ 1,101 Interest cost 46,027 44,229 43,440 1,859 1,695 1,745 3,180 2,999 2,829 Expected return on plan assets (56,558 ) (57,808 ) (53,342 ) — — — (3,149 ) (3,464 ) (3,264 ) Amortization of prior service cost — — — — — — 1,335 1,335 355 Amortization of net actuarial loss 25,266 32,743 22,873 1,383 1,293 783 417 345 — Net periodic benefit cost $ 37,568 $ 44,287 $ 34,331 $ 3,573 $ 3,308 $ 2,820 $ 3,282 $ 2,856 $ 1,021 Weighted-average assumptions (net benefit cost) Discount rate 4.50 % 4.25 % 5.00 % 4.50 % 4.25 % 5.00 % 4.50 % 4.25 % 5.00 % Expected return on plan assets 7.25 % 7.75 % 7.75 % N/A N/A N/A 7.25 % 7.75 % 7.75 % Weighted-average rate of compensation increase 3.25 % 2.75 % 3.25 % 3.25 % 2.75 % 3.25 % N/A N/A N/A Other Changes in Plan Assets and Benefit Obligations Recognized in Net Periodic Benefit Cost and Other Comprehensive Income 2016 2015 2014 Total Qualified SERP PBOP Total Qualified SERP PBOP Total Qualified SERP PBOP (Thousands of dollars) Net actuarial loss (gain) (a) $ 22,770 $ 25,153 $ 1,347 $ (3,730 ) $ 30,519 $ 26,949 $ 2,322 $ 1,248 $ 173,646 $ 163,215 $ 5,460 $ 4,971 Amortization of prior service cost (b) (1,335 ) — — (1,335 ) (1,335 ) — — (1,335 ) (355 ) — — (355 ) Amortization of net actuarial loss (b) (27,066 ) (25,266 ) (1,383 ) (417 ) (34,381 ) (32,743 ) (1,293 ) (345 ) (23,656 ) (22,872 ) (784 ) — Prior service cost — — — — — — — — 6,661 — — 6,661 Regulatory adjustment 5,584 102 — 5,482 5,646 5,214 — 432 (140,308 ) (129,031 ) — (11,277 ) Recognized in other comprehensive (income) loss (47 ) (11 ) (36 ) — 449 (580 ) 1,029 — 15,988 11,312 4,676 — Net periodic benefit costs recognized in net income 44,423 37,568 3,573 3,282 50,451 44,287 3,308 2,856 38,172 34,331 2,820 1,021 Total of amount recognized in net periodic benefit cost and other comprehensive (income) loss $ 44,376 $ 37,557 $ 3,537 $ 3,282 $ 50,900 $ 43,707 $ 4,337 $ 2,856 $ 54,160 $ 45,643 $ 7,496 $ 1,021 The table above discloses the net gain or loss and prior service cost recognized in other comprehensive income, separated into (a) amounts initially recognized in other comprehensive income, and (b) amounts subsequently recognized as adjustments to other comprehensive income as those amounts are amortized as components of net periodic benefit cost. See also Note 5 – Other Comprehensive Income and Accumulated Other Comprehensive Income (“AOCI”). U.S. GAAP states that a fair value measurement should be based on the assumptions that market participants would use in pricing the asset or liability and establishes a fair value hierarchy that ranks the inputs used to measure fair value by their reliability. The three levels of the fair value hierarchy are as follows: Level 1 – quoted prices (unadjusted) in active markets for identical assets or liabilities that a company has the ability to access at the measurement date. Level 2 – inputs other than quoted prices included within Level 1 that are observable for similar assets or liabilities, either directly or indirectly. Level 3 – unobservable inputs for the asset or liability. Unobservable inputs are used to measure fair value to the extent that observable inputs are not available, thereby allowing for situations in which there is little, if any, market activity for the asset or liability at the measurement date. The following table sets forth, by level within the three-level fair value hierarchy, the fair values of the assets of the qualified pension plan and the PBOP as of December 31, 2016 and December 31, 2015. The change in the types of pension investment holdings between years is due to the engagement of Russell and the subsequent transition of pension investments to Russell funds. The transition efforts consolidated the majority of the pension plan investments into private commingled equity and fixed income funds. The SERP has no assets. December 31, 2016 December 31, 2015 Qualified PBOP Total Qualified PBOP Total Assets at fair value (thousands of dollars): Level 1 – Quoted prices in active markets for identical financial assets Common stock Agriculture $ — $ — $ — $ 7,021 $ 209 $ 7,230 Capital equipment — — — 533 16 549 Chemicals/materials — — — 3,304 98 3,402 Consumer goods — — — 41,035 1,221 42,256 Energy and mining — — — 11,066 329 11,395 Finance/insurance — — — 29,957 892 30,849 Healthcare — — — 37,930 1,129 39,059 Information technology — — — 29,229 870 30,099 Services — — — 12,341 367 12,708 Telecommunications/internet/media — — — 25,883 770 26,653 Other — — — 9,043 269 9,312 Real estate investment trusts — — — 5,010 149 5,159 Mutual funds — 24,922 24,922 87,483 23,985 111,468 Government fixed income securities — — — 33,482 996 34,478 Futures contracts — — — (7 ) — (7 ) Total Level 1 Assets (1) $ — $ 24,922 $ 24,922 $ 333,310 $ 31,300 $ 364,610 Level 2 – Significant other observable inputs Private commingled equity funds (2) International $ 290,668 $ 9,140 $ 299,808 $ — $ — $ — Large and medium capitalization 121,434 3,819 125,253 — — — Small capitalization 25,947 816 26,763 — — — Emerging markets 45,309 1,424 46,733 — — — Private commingled fixed income funds (3) U.S. corporate bonds 161,086 5,066 166,152 — — — U.S. debt market long duration 77,349 2,432 79,781 — — — U.S. Treasury securities 8,665 272 8,937 — — — Pooled funds and mutual funds 4,889 216 5,105 14,808 796 15,604 Government fixed income and mortgage backed securities 167 5 172 49,571 1,475 51,046 Corporate fixed income securities Asset-backed and mortgage-backed — — — 23,542 701 24,243 Banking — — — 20,857 621 21,478 Insurance — — — 4,896 146 5,042 Utilities — — — 3,826 114 3,940 Other — — — 30,995 922 31,917 Real estate investment trusts — — — 1,949 58 2,007 State and local obligations — — — 950 28 978 Preferred securities — — — 554 17 571 Convertible securities — — — 196 6 202 Total Level 2 assets (4) $ 735,514 $ 23,190 $ 758,704 $ 152,144 $ 4,884 $ 157,028 Total Plan assets at fair value $ 735,514 $ 48,112 $ 783,626 $ 485,454 $ 36,184 $ 521,638 Commingled equity funds (5) — — — 250,511 7,455 257,966 Insurance company general account contracts (6) 3,448 — 3,448 3,719 — 3,719 Total Plan assets (7) $ 738,962 $ 48,112 $ 787,074 $ 739,684 $ 43,639 $ 783,323 (1) The Mutual funds category above is an intermediate-term bond fund whose manager employs multiple concurrent strategies and takes only moderate risk in each, thereby reducing the risk of poor performance arising from any single source, and a balanced fund that invests in a diversified portfolio of common stocks, preferred stocks and fixed-income securities. Strategies utilized by the bond fund include duration management, yield curve or maturity structuring, sector rotation, and all bottom-up in-house In the prior year, Level 1 also included Common stock, Real Estate Investment Trusts, Mutual funds, and U.S. Government securities listed or regularly traded on a national securities exchange and were valued at quoted market prices as of the last business day of the calendar year. (2) The private commingled equity funds include common collective trusts that invest in a diversified portfolio of domestic and international securities regularly traded on securities exchanges. These funds are shown in the above table at net asset value (“NAV”), which is the value of securities in the fund less the amount of any liabilities outstanding. Investment strategies employed by the funds include: • Domestic equities • International developed countries equities • Emerging markets equities Shares in the private equity commingled funds may be redeemed given one business day notice. While they are private equity funds and reported at NAV, due to the short redemption notice period, the lack of significant redemption fees, the fact that the underlying investments are exchange-traded, and that substantial liabilities do not exist subject to the NAV calculation, these investments are viewed as indirectly observable (level 2) and are also therefore, not excluded from the body of the fair value table as a reconciling item. Two funds are classified as international funds. One invests in international financial markets, primarily those of developed economies in Europe and the Pacific Basin. The fund invests primarily in equity securities issued by foreign corporations, but may invest in other securities perceived as offering attractive investment return opportunities. The other provides diversified exposure to global equity markets. The fund seeks to provide long-term capital growth by investing primarily in securities listed on the major developed equity markets of the United States, Europe, and Asia, as well as within those listed on emerging country equity markets on a tactical basis. The large and medium capitalization fund is designed to track the performance of the large and medium capitalization companies contained in the index, which represents approximately 90% of the market capitalization of the United States stock market. The small capitalization fund is designed to provide maximum long-term appreciation through investments that are well diversified by industry. The emerging markets fund was developed to invest in emerging market equities worldwide. The purposes of the fund’s operations, “emerging market countries” include every country in the world except the developed markets of the United States, Canada, Japan, Australia, New Zealand, Hong Kong and Singapore, and most countries located in Western Europe. Fund investments are made directly in each country or, where direct investment is inefficient or prohibited, through appropriate financial instruments or participation in commingled funds. (3) The private commingled fixed income funds include domestic fixed income securities. These funds are shown in the above table at NAV. Shares in the private commingled fixed equity funds may be redeemed given one business day notice. While they are private equity funds and reported at NAV, due to the short redemption notice period, the lack of significant redemption fees, the fact that the underlying investments are exchange-traded, and that substantial liabilities do not exist subject to the NAV calculation, these investments are viewed as indirectly observable (level 2) and are also therefore, not excluded from the body of the fair value table as a reconciling item. The U.S. corporate bond fund seeks to provide high quality, mostly corporate bond-based exposure to fixed income securities which closely match those found in discount curves used to value United States pension liabilities. The United States debt market long duration fund provides participation in the full spectrum of investment opportunities in primarily United States debt markets with longer maturities. The fund seeks to offer effective diversification against equities, take advantage of market trading opportunities, and provide a competitive rate of return on assets. The fund’s current duration is close to 14 years. The United States Treasuries securities funds seeks to replicate the risk and return characteristics of the Barclays Treasury U.S. Separate Trading of Registered Interest and Principal of Securities (“STRIPS”) 28-29 (4) With the exception of items (2) and (3), which are discussed in detail above, the current year Level 2 assets consist mainly of pooled funds and mutual funds. These funds are collective short-term funds that invest in Treasury bills and money market funds and are used as a temporary cash repository. In the prior year, the fair value of the Level 2 investments in debt securities with remaining maturities of one year or more was determined by dealers who make markets in such securities or by an independent pricing service, which considers yield or price of bonds of comparable quality, coupon, maturity, and type. (5) In the prior year, the commingled equity funds included private equity funds that invest in domestic and international securities regularly traded on securities exchanges. These funds are shown in the above table at net asset value, which is the value of securities in the fund less the amount of any liabilities outstanding. Investment strategies employed by the funds included: • Domestic large capitalization value equities • International developed countries value and growth equities • Emerging markets equities • International small capitalization equities The terms and conditions under which shares in the commingled equity funds were redeemed varied among the funds; the notice required ranged from one day to 30 days prior to the valuation date (month end). One of the commingled equity funds required the payment of a minimal impact fee to be applied to redemptions and subscriptions of $5 million or greater; the relative fee diminished the greater the transaction. Other such funds imposed fees to recover direct costs incurred by the fund at redemption, but were indeterminable prior to redemption. (6) The insurance company general account contracts are annuity insurance contracts used to pay the pensions of employees who retired prior to 1989. The balance of the account disclosed in the above table is the contract value, which is the result of deposits, withdrawals, and interest credits. (7) In the prior year, the assets in the above table exceeded the market value of plan assets shown in the funded status table by $2,859,000 (qualified retirement plan – $2,803,000, PBOP – $56,000), which includes a payable for securities purchased, partially offset by receivables for interest, dividends, and securities sold. |
Stock-Based Compensation
Stock-Based Compensation | 12 Months Ended |
Dec. 31, 2016 | |
Disclosure of Compensation Related Costs, Share-based Payments [Abstract] | |
Stock-Based Compensation | Note 11 – Stock-Based Compensation At December 31, 2016, two stock-based compensation plans existed: a performance share stock plan which includes a cash award, and a restricted stock/unit plan. All previous grants under the stock option plan expired in 2016. The table below shows total stock-based plan compensation expense, including the cash award, which was recognized in the Consolidated Statements of Income (in thousands): 2016 2015 2014 Stock-based compensation plan expense, net of related tax benefits $ 7,185 $ 7,278 $ 8,130 Stock-based compensation plan related tax benefits 4,404 4,461 4,983 Under the option plan, options to purchase shares of common stock at a stated exercise price were previously granted to key employees and outside directors. The last option grants were in 2006 and no future grants are anticipated. Each option had an exercise price equal to the market price of the Company’s common stock on the date of grant and a maximum term of ten years. The final options were exercised in 2016. The following tables summarize the stock option plan activity and related information (thousands of options): 2016 2015 2014 Number Weighted- Number of Weighted- Number of Weighted- Outstanding at the beginning of the year 17 $ 31.64 36 $ 28.97 52 $ 27.57 Exercised during the year (17 ) 31.64 (19 ) 26.69 (16 ) 24.31 Forfeited or expired during the year — — — — — — Outstanding and exercisable at year end — N/A 17 $ 31.64 36 $ 28.97 The intrinsic value of a stock option is the amount by which the market value of the underlying stock exceeds the exercise price of the option. The aggregate intrinsic value of outstanding and exercisable options, and options that were exercised, are presented in the table below (in thousands): 2016 2015 2014 Outstanding and exercisable $ — $ 394 $ 1,194 Exercised 554 590 451 December 31, 2016 December 31, 2015 December 31, 2014 Market value of Company stock $ 76.62 $ 55.16 $ 61.81 During 2016, $735,000 in cash was received from the exercise of options with a corresponding tax benefit of $205,000, which was recorded in additional paid-in Under the performance share stock plan, performance shares may be issued to encourage key employees to remain as employees and to achieve short-term and long-term performance goals. Plan participants are eligible to receive a cash bonus (i.e., short-term incentive) and performance shares (i.e., long-term incentive). The performance shares vest three years after grant and are then issued as common stock. Restricted stock/units under the restricted stock/unit plan are issued to attract, motivate, retain, and reward key employees with an incentive to attain high levels of individual performance and improved financial performance. The restricted stock/units vest 40% at the end of year one and 30% at the end of years two and three and are issued annually as common stock in accordance with the percentage vested. The restricted stock/unit plan was also established to attract, motivate, and retain experienced and knowledgeable independent directors. Vesting for grants of restricted stock/units to directors occurs immediately upon grant. The issuance of common stock for directors currently occurs when their service on the Board ends. The following table summarizes the activity of the performance share stock and restricted stock/unit plans as of December 31, 2016 (thousands of shares): Performance Weighted- Restricted Weighted- Nonvested/unissued at beginning of year 197 $ 50.63 228 $ 44.36 Granted 44 59.05 73 60.39 Dividends 5 6 Forfeited or expired — — — — Vested and issued* (78 ) 41.82 (45 ) 51.98 Nonvested/unissued at December 31, 2016 168 $ 55.62 262 $ 46.41 * Includes shares for retiree payouts and those converted for taxes. The weighted average grant date fair value of performance shares and restricted stock/units granted in 2015 and 2014 was $63.09 and $53.73, respectively. As of December 31, 2016, total compensation cost related to nonvested performance shares and restricted stock/units not yet recognized is $3.3 million. |
Income Taxes
Income Taxes | 12 Months Ended |
Dec. 31, 2016 | |
Income Tax Disclosure [Abstract] | |
Income Taxes | Note 12 – Income Taxes The following is a summary of income before taxes and noncontrolling interest for domestic and foreign operations (thousands of dollars): Year ended December 31, 2016 2015 2014 U.S. $ 218,810 $ 221,660 $ 221,471 Foreign 12,713 (2,328 ) (1,950 ) Total income before income taxes $ 231,523 $ 219,332 $ 219,521 Income tax expense (benefit) consists of the following (thousands of dollars): Year Ended December 31, 2016 2015 2014 Current: Federal $ 541 $ 21,321 $ 1,739 State 5,748 9,899 5,073 Foreign 4,298 650 2,193 10,587 31,870 9,005 Deferred: Federal 68,270 51,132 71,439 State 140 (2,574 ) 614 Foreign (529 ) (526 ) (2,685 ) 67,881 48,032 69,368 Total income tax expense $ 78,468 $ 79,902 $ 78,373 Deferred income tax expense (benefit) consists of the following significant components (thousands of dollars): Year Ended December 31, 2016 2015 2014 Deferred federal and state: Property-related items $ 76,217 $ 65,931 $ 52,814 Purchased gas cost adjustments 361 (32,993 ) 15,049 Employee benefits (1,327 ) 623 109 All other deferred (6,532 ) 15,332 2,257 Total deferred federal and state 68,719 48,893 70,229 Deferred ITC, net (838 ) (861 ) (861 ) Total deferred income tax expense $ 67,881 $ 48,032 $ 69,368 A reconciliation of the U.S. federal statutory rate to the consolidated effective tax rate for 2014, 2015, and 2016 (and the sources of these differences and the effect of each) are summarized as follows: Year Ended December 31, 2016 2015 2014 U.S. federal statutory income tax rate 35.0 % 35.0 % 35.0 % Net state taxes 1.4 1.8 1.9 Property-related items — 0.1 0.1 Tax credits (0.4 ) (0.4 ) (0.5 ) Company owned life insurance (1.2 ) 0.1 (1.0 ) All other differences (0.9 ) (0.2 ) 0.2 Consolidated effective income tax rate 33.9 % 36.4 % 35.7 % Deferred tax assets and liabilities consist of the following (thousands of dollars): December 31, 2016 2015 Deferred tax assets: Deferred income taxes for future amortization of ITC $ 1,094 $ 1,614 Employee benefits 38,231 36,923 Alternative minimum tax credit 4,827 4,809 Net operating losses and credits 1,204 868 Interest rate swap 6,080 7,351 Other 18,415 24,636 Valuation allowance (495 ) (499 ) 69,356 75,702 Deferred tax liabilities: Property-related items, including accelerated depreciation 872,136 794,850 Regulatory balancing accounts 1,104 743 Unamortized ITC 1,710 2,549 Debt-related costs 5,712 5,497 Intangibles 8,803 9,547 Other 19,256 31,533 908,721 844,719 Net noncurrent deferred tax liabilities $ 839,365 $ 769,017 The Company and its subsidiaries file income tax returns in the U.S. federal jurisdiction, various states, and in Canada. With few exceptions, the Company is no longer subject to United States federal, state and local, or Canadian income tax examinations for years before 2012. At December 31, 2016, the Company has U.S. federal net capital loss carryforwards of $278,000, which begin to expire in 2017. At December 31, 2016, the Company has an income tax net operating loss carryforward related to Canadian operations of $4.5 million which begins to expire in 2032. As of December 31, 2016, the Company has approximately $5 million of undistributed foreign earnings. However, management intends to permanently reinvest any future foreign earnings in Canada. A reconciliation of the beginning and ending amount of unrecognized tax benefits is as follows (thousands of dollars): 2016 2015 Unrecognized tax benefits at beginning of year $ 296 $ 305 Gross increases – tax positions in prior period 897 — Gross decreases – tax positions in prior period — (9 ) Gross increases – current period tax positions 38 — Gross decreases – current period tax positions — — Settlements — — Lapse in statute of limitations — — Unrecognized tax benefits at end of year $ 1,231 $ 296 In assessing whether uncertain tax positions should be recognized in its financial statements, management first determines whether it is more-likely-than-not more-likely-than-not more-likely-than-not more-likely-than-not The total amount of unrecognized tax benefits that, if recognized, would impact the effective tax rate was $935,000 at December 31, 2016. No significant increases or decreases in unrecognized tax benefit are expected within the next 12 months. The Company recognizes interest expense and income and penalties related to income tax matters in income tax expense. There was no tax-related Income Tax Regulations |
Derivatives and Fair Value Meas
Derivatives and Fair Value Measurements | 12 Months Ended |
Dec. 31, 2016 | |
Fair Value Disclosures [Abstract] | |
Derivatives and Fair Value Measurements | Note 13 – Derivatives and Fair Value Measurements Derivatives. fixed-for-floating 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 25% in the Arizona and California jurisdictions) of its natural gas supply portfolios. The maturities of the Swaps highly correlate to forecasted purchases of natural gas, during time frames ranging from January 2017 through March 2019. Under such contracts, Southwest pays the counterparty 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): December 31, 2016 December 31, 2015 Contract notional amounts 10,543 7,407 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 Southwest’s Swaps (derivatives) for the years ended December 31, 2016, 2015, and 2014 and their location in the Consolidated Statements of Income: Gains (losses) recognized in income for derivatives not designated as hedging instruments: (Thousands of dollars) Instrument Location of Gain or (Loss) 2016 2015 2014 Swaps Net cost of gas sold $ 5,006 $ (7,598 ) $ (2,363 ) Swaps Net cost of gas sold (5,006 )* 7,598 * 2,363 * Total $ — $ — $ — * Represents the impact of regulatory deferral accounting treatment under U.S. GAAP for rate-regulated entities. No gains (losses) were recognized in net 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”), both of which were designated cash flow hedges, to partially hedge the risk of interest rate variability during the period leading up to the planned issuance of debt. The first FSIRS terminated in December 2010, and the second, in March 2012. Losses on both FSIRS are being amortized over ten-year The following table sets forth the fair values of the Swaps and their location in the Consolidated Balance Sheets (thousands of dollars): Fair values of derivatives not designated as hedging instruments: December 31, 2016 Instrument Balance Sheet Location Asset Liability Net Swaps Deferred charges and other assets $ 899 $ (54 ) $ 845 Swaps Prepaids and other current assets 3,551 (19 ) 3,532 Total $ 4,450 $ (73 ) $ 4,377 December 31, 2015 Instrument Balance Sheet Location Asset Liability Net Swaps Other current liabilities $ — $ (4,267 ) $ (4,267 ) Swaps Other deferred credits 4 (1,223 ) (1,219 ) Total $ 4 $ (5,490 ) $ (5,486 ) The estimated fair values of the natural gas derivatives were determined using future natural gas index prices (as more fully described below). Master netting arrangements exist with each counterparty that provide for the net settlement (in the settlement month) of all contracts through a single payment. As applicable, management has elected to reflect the net amounts in its balance sheets. No outstanding collateral associated with the Swaps existed during any period presented in the above table. Pursuant to regulatory deferral accounting treatment for rate-regulated entities, unrealized gains and losses in fair value of the Swaps are recorded as a regulatory asset and/or liability. When the Swaps mature, any prior positions held are reversed and the settled position is recorded 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 presents the amounts paid to and received from counterparties for settlements of matured Swaps. Year ended Year ended Year ended (Thousands of dollars) Paid to counterparties $ 5,583 $ 7,537 $ 829 Received from counterparties $ 726 $ — $ 4,713 The following table details the regulatory assets/(liabilities) offsetting the derivatives at fair value in the Consolidated Balance Sheets (thousands of dollars). December 31, 2016 Instrument Balance Sheet Location Net Total Swaps Other deferred credits $ (845 ) Swaps Other current liabilities (3,532 ) December 31, 2015 Instrument Balance Sheet Location Net Total Swaps Prepaids and other current assets $ 4,267 Swaps Deferred charges and other assets 1,219 Fair Value Measurements. 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, financial assets and liabilities that were accounted for at fair value (see Note 10 – Pension and Other Post Retirement Benefits for definitions of the levels of the fair value hierarchy): Level 2 – Significant other observable inputs December 31, 2016 December 31, 2015 (Thousands of dollars) Assets at fair value: Prepaids and other current assets – Swaps $ 3,532 $ — Deferred charges and other assets – Swaps 845 — Liabilities at fair value: Other current liabilities – Swaps — (4,267 ) Other deferred credits – Swaps — (1,219 ) Net Assets (Liabilities) $ 4,377 $ (5,486 ) No financial assets or liabilities associated with the Swaps, which were accounted for at fair value, fell within Level 1 or Level 3 of the fair value hierarchy. With regard to the fair values of assets associated with pension and postretirement benefit plans, refer to Note 10 – Pension and Other Post Retirement Benefits . |
Segment Information
Segment Information | 12 Months Ended |
Dec. 31, 2016 | |
Segment Reporting [Abstract] | |
Segment Information | Note 14 – Segment Information Operating segments are determined based on the nature of their activities. The natural gas operations segment is engaged in the business of purchasing, distributing, and transporting natural gas. Revenues are generated from the distribution and transportation of natural gas. The construction services segment is primarily engaged in the business of providing utility companies with trenching and installation, replacement, and maintenance services for energy distribution systems, and providing industrial construction solutions. Over 99% of the total Company’s long-lived assets are in the United States. The accounting policies of the reported segments are the same as those described within Note 1 – Summary of Significant Accounting Policies . Centuri accounts for the services provided to Southwest at contractual prices at contract inception. Accounts receivable for these services, which are not eliminated during consolidation, are presented in the table below (in thousands). December 31, 2016 December 31, 2015 Accounts receivable for Centuri services $ 10,585 $ 10,006 The following table presents the amount of revenues for both segments by geographic area (thousands of dollars): December 31, December 31, December 31, Revenues (a) United States $ 2,256,600 $ 2,289,133 $ 2,069,513 Canada 203,890 174,492 52,194 Total $ 2,460,490 $ 2,463,625 $ 2,121,707 (a) Revenues are attributed to countries based on the location of customers. The financial information pertaining to the natural gas operations and construction services segments for each of the three years in the period ended December 31, 2016 is as follows (thousands of dollars): 2016 Gas Construction Adjustments Total Revenues from unaffiliated customers $ 1,321,412 $ 1,040,957 $ 2,362,369 Intersegment sales — 98,121 98,121 Total $ 1,321,412 $ 1,139,078 $ 2,460,490 Interest revenue $ 1,848 $ 1 $ 1,849 Interest expense $ 66,997 $ 6,663 $ 73,660 Depreciation and amortization $ 233,463 $ 55,669 $ 289,132 Income tax expense $ 58,584 $ 19,884 $ 78,468 Segment net income $ 119,423 $ 32,618 $ 152,041 Segment assets $ 5,001,756 $ 579,370 $ 5,581,126 Capital expenditures $ 457,120 $ 72,411 $ 529,531 2015 Gas Construction Adjustments Total Revenues from unaffiliated customers $ 1,454,639 $ 904,870 $ 2,359,509 Intersegment sales — 104,116 104,116 Total $ 1,454,639 $ 1,008,986 $ 2,463,625 Interest revenue $ 1,754 $ 419 $ 2,173 Interest expense $ 64,095 $ 7,784 $ 71,879 Depreciation and amortization $ 213,455 $ 56,656 $ 270,111 Income tax expense $ 61,355 $ 18,547 $ 79,902 Segment net income $ 111,625 $ 26,692 $ 138,317 Segment assets $ 4,822,845 $ 535,840 $ 5,358,685 Capital expenditures $ 438,289 $ 49,711 $ 488,000 2014 Gas Construction Adjustments (a) Total Revenues from unaffiliated customers $ 1,382,087 $ 647,432 $ 2,029,519 Intersegment sales — 92,188 92,188 Total $ 1,382,087 $ 739,620 $ 2,121,707 Interest revenue $ 2,596 $ 6 $ 2,602 Interest expense $ 68,299 $ 3,770 $ 72,069 Depreciation and amortization $ 204,144 $ 48,883 $ 253,027 Income tax expense $ 63,597 $ 14,776 $ 78,373 Segment net income $ 116,872 $ 24,254 $ 141,126 Segment assets $ 4,652,307 $ 566,589 $ (10,599 ) $ 5,208,297 Capital expenditures $ 350,025 $ 46,873 $ 396,898 (a) Construction services segment assets included two liabilities that were netted against gas operations segment assets during consolidation in 2014. They are: Income taxes payable of $3.3 million, netted against income taxes receivable, net and deferred income taxes of $1.4 million, netted against deferred income taxes, net. Construction services segment assets exclude a long-term deferred tax benefit of $1.4 million, which was netted against gas operations segment deferred income taxes and investment tax credits, net during consolidation. Gas operations segment assets include a deferred income tax liability of $4.5 million, which was netted against a construction services segment asset for deferred income taxes, net during consolidation. |
Quarterly Financial Data
Quarterly Financial Data | 12 Months Ended |
Dec. 31, 2016 | |
Quarterly Financial Information Disclosure [Abstract] | |
Quarterly Financial Data | Note 15 – Quarterly Financial Data (Unaudited) Quarter Ended March 31 June 30 September 30 December 31 (Thousands of dollars, except per share amounts) 2016 Operating revenues $ 731,248 $ 547,748 $ 539,969 $ 641,525 Operating income 134,096 28,116 15,539 117,963 Net income 75,355 9,099 2,907 65,694 Net income attributable to Southwest Gas Corporation 75,446 8,943 2,472 65,180 Basic earnings per common share* 1.59 0.19 0.05 1.37 Diluted earnings per common share* 1.58 0.19 0.05 1.36 2015 Operating revenues $ 734,220 $ 538,604 $ 505,396 $ 685,405 Operating income 129,556 25,047 16,143 117,586 Net income (loss) 71,879 5,063 (4,210 ) 66,698 Net income (loss) attributable to Southwest Gas Corporation 71,983 4,949 (4,734 ) 66,119 Basic earnings (loss) per common share* 1.54 0.11 (0.10 ) 1.40 Diluted earnings (loss) per common share* 1.53 0.10 (0.10 ) 1.38 2014 Operating revenues $ 608,396 $ 453,153 $ 432,475 $ 627,683 Operating income 127,065 26,755 18,290 112,373 Net income 70,697 9,627 1,927 58,897 Net income attributable to Southwest Gas Corporation 70,783 9,627 1,970 58,746 Basic earnings per common share* 1.52 0.21 0.04 1.26 Diluted earnings per common share* 1.51 0.21 0.04 1.25 * The sum of quarterly earnings (loss) per average common share may not equal the annual earnings (loss) per share due to the ongoing change in the weighted-average number of common shares outstanding. The demand for natural gas is seasonal, and it is the opinion of management that comparisons of earnings for interim periods do not reliably reflect overall trends and changes in operations. Also, the timing of general rate relief can have a significant impact on earnings for interim periods. See Management’s Discussion and Analysis for additional discussion of operating results. |
Construction Services Noncontro
Construction Services Noncontrolling Interests | 12 Months Ended |
Dec. 31, 2016 | |
Noncontrolling Interest [Abstract] | |
Construction Services Noncontrolling Interests | Note 16 – Construction Services Noncontrolling Interests Associated with the agreement reached in conjunction with the acquisition of the Canadian construction businesses in October 2014, the previous owners of the acquired companies initially retained an approximate 10% equity interest in the Canadian-specific businesses, and special dividend rights which entitled the sellers, as holders, to dividends equal to 3.4% of dividends paid at the level of Centuri, and subject to certain conditions, such interests could become exchangeable for a 3.4% equity interest in Centuri. In consideration of the underlying exchange rights of the original agreement, earnings attribution by Centuri to the previous owners also occurred in an amount equivalent to 3.4% of Centuri earnings since October 2014. During the third quarter of 2015, the sellers formally exercised their exchange rights under the terms of the original agreement. No new rights were conveyed to the noncontrolling parties as a result of the exchange and no new consideration was involved. The previous owners are currently eligible to exit their investment retained by requiring the purchase of a portion of their interest and in incremental amounts annually. The shares subject to the election cumulate (if earlier elections are not made) such that 100% of their interest retained is subject to the election beginning in July 2022. Due to the ability of the noncontrolling parties to redeem their interest in Centuri for cash, their collective interest is presented on the Consolidated Balance Sheets at December 31, 2016 and December 31, 2015 as a Redeemable noncontrolling interest, a category of mezzanine equity (temporary equity), in accordance with SEC guidance. Significant changes in the value of the redeemable noncontrolling interest are recognized as they occur, and the carrying value is adjusted as necessary at each reporting date. Guidance by the SEC indicates that downward adjustments in the value of redeemable noncontrolling interests are only permitted to the extent that upward adjustments in value were previously recognized. A floor for the noncontrolling interest was originally set at the acquisition date (in October 2014). However, U.S. GAAP generally views changes in ownership interest, where the parent retains its controlling interest, as an equity transaction, whereby the carrying amount of the noncontrolling interest is adjusted to reflect the change in ownership interest in the subsidiary. In connection with the exchange rights exercised during the third quarter of 2015, an updated valuation was conducted. A significant decrease in the value of the redeemable noncontrolling interest was recognized at that time, due in part to the exchange option no longer being subject to probability estimates. In light of the U.S. GAAP requirement to adjust the carrying amount, a new floor was set for the redeemable noncontrolling interest at the exchange date (July 31, 2015), with a corresponding adjustment made to additional paid-in Redeemable (Thousands of dollars): Balance, December 31, 2015 $ 16,108 Net Income (loss) attributable to redeemable noncontrolling interest 1,148 Foreign currency exchange translation adjustment 5 Centuri distribution to redeemable noncontrolling interest (439 ) Adjustment to redemption value 5,768 Balance, December 31, 2016 $ 22,590 The redemption value of the redeemable noncontrolling interest utilizes a market approach to determine a construction services enterprise value. Publicly traded “guideline” companies are identified by using a selection criteria, including actively traded equities, their financial solvency, and other factors. Once the guideline companies are determined, enterprise value is calculated using a weighted approach of projected earnings before interest expense and taxes (“EBIT”) and earnings before interest expense, taxes, and depreciation and amortization expense (“EBITDA”). After an estimated fair value is determined, it is multiplied by 3.4%. A discount is then applied due to limitations of the nonpublic noncontrolling interest being valued. Each quarter, market changes in the guideline companies are considered and the weighted approach to projected EBIT and EBITDA, in relation to the guideline companies, is re-evaluated Centuri also holds a 65% interest in a venture to market natural gas engine-driven heating, ventilating, and air conditioning (“HVAC”) technology and products. Centuri consolidates the entity (IntelliChoice Energy, LLC) as a majority-owned subsidiary. The interest is immaterial to the consolidated financial statements, but is identified as the Noncontrolling interest within Total equity on the Consolidated Balance Sheets. |
Summary of Significant Accoun25
Summary of Significant Accounting Policies (Policies) | 12 Months Ended |
Dec. 31, 2016 | |
Accounting Policies [Abstract] | |
Holding Company Reorganization | Holding Company Reorganization. one-for-one |
Nature of Operations | Nature of Operations. Acquisition of Construction Services Businesses |
Basis of Presentation | Basis of Presentation. |
Consolidation | Consolidation. Centuri, through its subsidiaries, holds a 65% interest in a venture to market natural gas engine-driven heating, ventilating, and air conditioning (“HVAC”) technology and products. Centuri consolidates the entity (IntelliChoice Energy, LLC). Centuri, through its subsidiaries, holds a 50% interest in W.S. Nicholls Western Construction LTD. (“Western”), a Canadian construction services company that is a variable interest entity. Centuri determined that it is not the primary beneficiary of the entity due to a shared-power structure; therefore, Centuri does not consolidate the entity and has recorded its investment, and results related thereto, using the equity method. The investment in Western totaled $10.8 million at December 31, 2015 and 2016. Both periods include the impacts of foreign currency exchange translation adjustments. Dividends of $500,000 were received from Western during 2016 with no impact on earnings. No dividends were received from Western in 2015. A management fee was paid by Western to its partners, including W.S. Nicholls, in accordance with underlying agreements. The equity method investment in Western is included in Other Property and Investments in the Consolidated Balance Sheets. Centuri’s maximum exposure to loss as a result of its involvement with Western is estimated at $35.8 million. The estimated maximum exposure to loss represents the maximum loss that would be absorbed by Centuri in the event that all of the assets of Western were deemed to be worthless. Centuri recorded earnings of $69,000 from this investment in 2016, which is included in Other Income (deductions) in the Consolidated Statements of Income. In addition, Centuri, through its subsidiaries, has a 25% interest in CCI-TBN |
Net Utility Plant | Net Utility Plant. |
Other Property and Investments | Other Property and Investments. 2016 2015 Centuri property, equipment, and intangibles $ 451,114 $ 423,369 Centuri accumulated provision for depreciation and amortization (228,374 ) (221,028 ) Net cash surrender value of COLI policies 106,744 99,276 Other property 12,859 11,914 Total $ 342,343 $ 313,531 |
Deferred Purchased Gas Costs | Deferred Purchased Gas Costs. |
Prepaids and Other Current Assets | Prepaids and other current assets |
Income Taxes | Income Taxes. |
Cash and Cash Equivalents | Cash and Cash Equivalents. Significant non-cash non-cash non-cash non-cash |
Goodwill | Goodwill. th Natural Construction Consolidated (In thousands of dollars) December 31, 2015 $ 10,095 $ 116,050 $ 126,145 Additional goodwill from ETTI acquisition — 10,726 10,726 Foreign currency translation adjustment — 3,112 3,112 December 31, 2016 $ 10,095 $ 129,888 $ 139,983 Goodwill from the ETTI acquisition consists of the excess of purchase price over the fair value of the acquired net assets and represents the value of the assembled workforce and the estimated economic value attributable to future opportunities that will arise based on the strong financial performance of the combined entities. |
Acquisition of Construction Services Businesses | Acquisition of Construction Services Businesses. Assets acquired in the transaction were recorded at their acquisition date fair values. The final purchase accounting is complete. The final estimated fair values of assets acquired as of May 6, 2016, the acquisition date, are as follows (in millions of dollars): Acquisition Property, plant and equipment $ 4.3 Intangible assets 2.9 Goodwill 10.7 Total assets acquired $ 17.9 The purchase price consisted of $17 million in cash on the acquisition date with the remaining amount being deferred over four years. |
Intangible Assets | Intangible Assets December 31, 2016 Gross Carrying Accumulated Net Carrying Customer relationships $ 34,033 $ (3,906 ) $ 30,127 Trade names and trademarks 9,349 (2,565 ) 6,784 Customer contracts backlog 1,656 (1,656 ) — Noncompete agreement 1,029 (271 ) 758 Total $ 46,067 $ (8,398 ) $ 37,669 December 31, 2015 Customer relationships $ 31,226 $ (2,070 ) $ 29,156 Trade names and trademarks 8,621 (1,331 ) 7,290 Customer contracts backlog 1,606 (1,606 ) — Noncompete agreement 437 (110 ) 327 Total $ 41,890 $ (5,117 ) $ 36,773 The intangible assets (other than goodwill and software-related intangibles) are included in Other property and investments in the Consolidated Balance Sheets. The estimated future amortization of the intangible assets for the next five years is as follows (in thousands): 2017 $ 3,339 2018 3,126 2019 2,463 2020 2,395 2021 2,269 See Note 2 – Utility Plant and Leases for additional information regarding natural gas operations intangible assets. |
Accumulated Removal Costs | Accumulated Removal Costs. |
Gas Operating Revenues | Gas Operating Revenues. The Company acts as an agent for state and local taxing authorities in the collection and remission of a variety of taxes, including sales and use taxes and surcharges. These taxes are not included in gas operating revenues. Management uses the net classification method to report taxes collected from customers to be remitted to governmental authorities. |
Construction Revenues | Construction Revenues. percentage-of-completion |
Construction Expenses | Construction Expenses. job-related |
Net Cost of Gas Sold | Net Cost of Gas Sold. |
Operations and Maintenance Expense | Operations and Maintenance Expense. |
Depreciation and Amortization | Depreciation and Amortization. Accumulated Removal Costs |
Allowance for Funds Used During Construction ("AFUDC") | Allowance for Funds Used During Construction (“AFUDC”). 2016 2015 2014 (In thousands) AFUDC: Debt portion $ 1,175 $ 1,666 $ 1,228 Equity portion 2,289 3,008 1,995 AFUDC capitalized as part of utility plant $ 3,464 $ 4,674 $ 3,223 AFUDC rate 7.35 % 7.32 % 7.73 % |
Other Income (Deductions) | Other Income (Deductions). 2016 2015 2014 Change in COLI policies $ 7,400 $ (500 ) $ 5,300 Interest income 1,849 2,173 2,602 Equity AFUDC 2,289 3,008 1,995 Foreign currency transaction gain (loss) (22 ) (824 ) (178 ) Equity in earnings of unconsolidated investment - Western 69 310 107 Miscellaneous income and (expense) (2,116 ) (1,288 ) (2,719 ) Total other income (deductions) $ 9,469 $ 2,879 $ 7,107 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 the Company 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 |
Foreign Currency Translation | Foreign Currency Translation. |
Earnings Per Share | Earnings Per Share. 2016 2015 2014 (In thousands) Average basic shares 47,469 46,992 46,494 Effect of dilutive securities: Stock options 1 8 17 Performance shares 124 171 215 Restricted stock units 220 212 218 Average diluted shares 47,814 47,383 46,944 |
Recently Issued Accounting Standards Updates | Recently Issued Accounting Standards Updates. one-year Management has substantially completed the evaluation of the sources of revenue and are currently assessing the effect of the new guidance on the financial position, results of operations and cash flows. The assessment is contingent, in part, upon the completion of deliberations currently in progress by the utility industry, notably in connection with efforts to produce an accounting guide intended to be developed by the American Institute of Certified Public Accountants (“AICPA”). In association with this undertaking, the AICPA formed a number of industry task forces, including a Power & Utilities (“P&U”) Task Force, on which Company personnel actively participate via formal membership. Industry representatives and organizations, the largest auditing firms, the AICPA’s Revenue Recognition Working Group and its Financial Reporting Executive Committee have undertaken, and continue to undertake, consideration of several items relevant to the utility industry. Where applicable or necessary, the FASB’s Transition Resource Group (TRG) is also participating. Currently, the industry is working to address several items including the evaluation of collectability from customers if a utility has regulatory mechanisms to help assure recovery of uncollected accounts from ratepayers and the accounting for funds received from third parties to partially or fully reimburse the cost of construction of an asset. Currently, a timeline for the resolution of these deliberations has not been established. Southwest is actively working with its peers in the rate-regulated natural gas industry and with the public accounting profession to conclude on the accounting treatment for several other issues that are not expected to be addressed by the P&U Task Force. As of December 31, 2016, the construction services segment has substantially completed the evaluation of sources of revenue and is currently assessing the effect of the new guidance on financial position, results of operations and cash flows. The principals of the new revenue recognition guidance are very similar to existing guidance for construction contractors. Similar to the P&U Task Force noted above, the AICPA formed the Engineering and Construction Contractors Task Force to assist the construction industry with implementing the new guidance. The accounting guide the AICPA intends to release is expected to provide implementation guidance related to several issues including 1) combining contracts and separating performance obligations; 2) estimating change orders, incentives, penalties, liquidated damages and other variable consideration items and 3) acceptable measures of progress when recognizing revenue over time. Given the uncertainty with respect to the conclusions that might arise from the deliberations on issues associated with both the natural gas and construction services segments, the Company is currently unable to determine the effect the new guidance will have on its financial position, results of operations, cash flows, business processes, or the transition method it will utilize to adopt the new guidance. In January 2016, the FASB issued the update “Financial Instruments – Overall (Subtopic 825-10): In February 2016, the FASB issued the update “Leases (Topic 842)”. Under the update, lessees will be required to recognize the following for all leases (with the exception of short-term leases) at the commencement date: • A lease liability, which is a lessee’s obligation to make lease payments arising from a lease, measured on a discounted basis; and • A right-of-use Under the new guidance, lessor accounting is largely unchanged. Certain targeted improvements were made to align, where necessary, lessor accounting with the lessee accounting model and Topic 606, Revenue from Contracts with Customers. Though companies have historically been required to make disclosures regarding leases and of contractual obligations, leases (with terms longer than a year) will no longer exist off-balance In March 2016, the FASB issued the update “Compensation – Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting”. The amendments are intended to improve the accounting for employee share-based payments and affect all organizations that issue share-based payment awards to their employees. The update requires the recording of all of the tax effects related to share-based payments at settlement (or expiration) through the income statement. Currently, tax benefits in excess of compensation cost (“windfalls”) are recorded in equity, and tax deficiencies (“shortfalls”) are recorded in equity to the extent of previous windfalls, and then recorded in the income statement. While the simplification will reduce some of the administrative complexities by eliminating the need to track a “windfall pool,” it will increase the volatility of income tax expense. The update also allows entities to withhold shares for the employee tax burden up to the employees’ maximum individual tax rate in the relevant jurisdiction without resulting in a liability classification of the award (currently such withholding is limited to the employer’s minimum statutory withholding). The update clarifies that all cash payments made to taxing authorities on the employees’ behalf for withheld shares should be presented as financing activities on the statement of cash flows. Also, the update requires all tax-related In June 2016, the FASB issued the update “Financial Instruments – Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments”. The update amends guidance on reporting credit losses for financial assets held at amortized cost basis and available for sale debt securities. For assets held at amortized cost basis, the update eliminates the “probable” threshold for initial recognition of credit losses in current U.S. GAAP and, instead, requires an entity to reflect its current estimate of all expected credit losses. The allowance for credit losses is a valuation account that is deducted from the amortized cost basis of the financial asset to present the net amount expected to be collected. For available for sale debt securities, credit losses should be measured in a manner similar to current U.S. GAAP, however the update will require that credit losses be presented as an allowance rather than as a write-down. This update affects entities holding financial assets and net investment in leases that are not accounted for at fair value through net income. The update affects loans, debt securities, trade receivables, net investments in leases, off-balance In August 2016, the FASB issued the update “Classification of Certain Cash Receipts and Cash Payments”. This update addresses the following specific cash flow issues: debt prepayment or debt extinguishment costs; settlement of zero-coupon In October 2016, the FASB issued the update “Accounting for Income Taxes: Intra-Entity Asset Transfers of Assets Other than Inventory.” This update eliminates the current U.S. GAAP exception for all intra-entity sales of assets other than inventory. As a result, a reporting entity would recognize the tax expense from the sale of the asset in the seller’s tax jurisdiction when the transfer occurs, even though the pre-tax In October 2016, the FASB issued the update “Consolidation (Topic 810): Interests Held through Related Parties That Are under Common Control.” The amendments affect reporting entities that are required to evaluate whether they should consolidate a variable interest entity in certain situations involving entities under common control. The update is effective for fiscal and interim periods beginning after December 15, 2016. Management has determined that this update is not impactful to its consolidated financial statements. In January 2017, the FASB issued the update “Intangibles – Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment.” The update eliminates Step 2 from the goodwill impairment test. The annual, or interim, goodwill impairment test is performed by comparing the fair value of a reporting unit with its carrying amount. An impairment charge should be recognized for the amount by which the carrying amount exceeds the reporting unit’s fair value; however, the loss recognized should not exceed the total amount of goodwill allocated to that reporting unit. In addition, income tax effects from any tax deductible goodwill on the carrying amount of the reporting unit should be considered when measuring the goodwill impairment loss, if applicable. The update also eliminates the requirements for any reporting unit with a zero or negative carrying amount to perform a qualitative assessment and, if it fails that qualitative test, to perform Step 2 of the goodwill impairment test. An entity still has the option to perform the qualitative assessment for a reporting unit to determine if the quantitative impairment test is necessary. The amendments should be applied on a prospective basis. The update is effective for fiscal and interim periods beginning after December 15, 2019. Early adoption is permitted for interim or annual goodwill impairment tests performed on testing dates after January 1, 2017. Management has determined that this update would have had no impact on the consolidated financial statements for the periods presented if it had been effective during those periods. |
Subsequent Events | Subsequent Events. |
Summary of Significant Accoun26
Summary of Significant Accounting Policies (Tables) | 12 Months Ended |
Dec. 31, 2016 | |
Accounting Policies [Abstract] | |
Schedule of Other Property and Investments | Other Property and Investments. 2016 2015 Centuri property, equipment, and intangibles $ 451,114 $ 423,369 Centuri accumulated provision for depreciation and amortization (228,374 ) (221,028 ) Net cash surrender value of COLI policies 106,744 99,276 Other property 12,859 11,914 Total $ 342,343 $ 313,531 |
Schedule of Goodwill | Natural Construction Consolidated (In thousands of dollars) December 31, 2015 $ 10,095 $ 116,050 $ 126,145 Additional goodwill from ETTI acquisition — 10,726 10,726 Foreign currency translation adjustment — 3,112 3,112 December 31, 2016 $ 10,095 $ 129,888 $ 139,983 |
Estimated Fair Values of Assets Acquired as of Acquisition Date | The final estimated fair values of assets acquired as of May 6, 2016, the acquisition date, are as follows (in millions of dollars): Acquisition Property, plant and equipment $ 4.3 Intangible assets 2.9 Goodwill 10.7 Total assets acquired $ 17.9 |
Summary of Intangible Assets | Centuri has $37.7 million and $36.8 million of intangible assets (varies due to foreign currency translation) at December 31, 2016 and 2015, respectively, as detailed in the following table (thousands of dollars): December 31, 2016 Gross Carrying Accumulated Net Carrying Customer relationships $ 34,033 $ (3,906 ) $ 30,127 Trade names and trademarks 9,349 (2,565 ) 6,784 Customer contracts backlog 1,656 (1,656 ) — Noncompete agreement 1,029 (271 ) 758 Total $ 46,067 $ (8,398 ) $ 37,669 December 31, 2015 Customer relationships $ 31,226 $ (2,070 ) $ 29,156 Trade names and trademarks 8,621 (1,331 ) 7,290 Customer contracts backlog 1,606 (1,606 ) — Noncompete agreement 437 (110 ) 327 Total $ 41,890 $ (5,117 ) $ 36,773 |
Schedule of Estimated Future Amortization of Intangible Assets | The intangible assets (other than goodwill and software-related intangibles) are included in Other property and investments in the Consolidated Balance Sheets. The estimated future amortization of the intangible assets for the next five years is as follows (in thousands): 2017 $ 3,339 2018 3,126 2019 2,463 2020 2,395 2021 2,269 |
Schedule of Capitalized and Debt Portion of AFUDC | Utility plant construction costs, including AFUDC, are recovered in authorized rates through depreciation when completed projects are placed into operation, and general rate relief is requested and granted. 2016 2015 2014 (In thousands) AFUDC: Debt portion $ 1,175 $ 1,666 $ 1,228 Equity portion 2,289 3,008 1,995 AFUDC capitalized as part of utility plant $ 3,464 $ 4,674 $ 3,223 AFUDC rate 7.35 % 7.32 % 7.73 % |
Other Income (Deductions) | The following table provides the composition of significant items included in Other income (deductions) on the consolidated statements of income (thousands of dollars): 2016 2015 2014 Change in COLI policies $ 7,400 $ (500 ) $ 5,300 Interest income 1,849 2,173 2,602 Equity AFUDC 2,289 3,008 1,995 Foreign currency transaction gain (loss) (22 ) (824 ) (178 ) Equity in earnings of unconsolidated investment - Western 69 310 107 Miscellaneous income and (expense) (2,116 ) (1,288 ) (2,719 ) Total other income (deductions) $ 9,469 $ 2,879 $ 7,107 |
Schedule of Earnings Per Share, Basic and Diluted | A reconciliation of the denominator used in the Basic and Diluted EPS calculations is shown in the following table. 2016 2015 2014 (In thousands) Average basic shares 47,469 46,992 46,494 Effect of dilutive securities: Stock options 1 8 17 Performance shares 124 171 215 Restricted stock units 220 212 218 Average diluted shares 47,814 47,383 46,944 |
Utility Plant and Leases (Table
Utility Plant and Leases (Tables) | 12 Months Ended |
Dec. 31, 2016 | |
Leases [Abstract] | |
Schedule of Net Utility Plant | Net utility plant as of December 31, 2016 and 2015 was as follows (thousands of dollars): December 31, 2016 2015 Gas plant: Storage $ 24,614 $ 22,944 Transmission 349,981 312,996 Distribution 5,198,531 4,935,730 General 382,084 365,865 Software and software-related intangibles 224,260 203,323 Other 14,094 14,059 6,193,564 5,854,917 Less: accumulated depreciation (2,172,966 ) (2,084,007 ) Acquisition adjustments, net 196 370 Construction work in progress 111,177 119,805 Net utility plant $ 4,131,971 $ 3,891,085 |
Schedule of Depreciation and Amortization Expense | Depreciation and amortization expense on gas plant, including intangibles, was as follows (thousands of dollars): 2016 2015 2014 Depreciation and amortization expense $ 214,037 $ 201,233 $ 194,360 |
Schedule of Rental Payments for Operating Leases | The table below presents Southwest’s rental payments and Centuri’s lease payments that are included in operating expenses (in thousands): 2016 2015 2014 Southwest Gas $ 4,357 $ 4,186 $ 5,330 Centuri 53,956 45,849 30,012 Consolidated rental payments/lease expense $ 58,313 $ 50,035 $ 35,342 |
Schedule of Future Minimum Lease Payments for Operating Leases | The following is a schedule of future minimum lease payments for significant non-cancelable Year Ending December 31, 2017 $ 6,929 2018 4,837 2019 3,449 2020 2,411 2021 1,098 Thereafter 2,730 Total minimum lease payments $ 21,454 |
Schedule of Capital Leases of Equipment | The amounts associated with capital leases of equipment as of December 31, 2016 and 2015 are as follows (thousands of dollars): December 31, 2016 2015 Capital leased assets, gross $ 3,189 $ 4,584 Less: accumulated amortization (1,172 ) (1,043 ) Capital leased assets, net $ 2,017 $ 3,541 |
Schedule of Future Minimum Lease Payments for Capital Leases | The following is a schedule of future minimum lease payments for non-cancelable Year Ending December 31, 2017 $ 931 2018 546 2019 84 2020 — 2021 — Thereafter — 1,561 Less: amount representing interest (101 ) Total minimum lease payments $ 1,460 |
Receivables and Related Allow28
Receivables and Related Allowances (Tables) | 12 Months Ended |
Dec. 31, 2016 | |
Receivables [Abstract] | |
Schedule of Accounts Receivable | The table below contains information about the gas utility customer accounts receivable balance (net of allowance) at December 31, 2016 and 2015, and the percentage of customers in each of the three states. December 31, December 31, Gas utility customer accounts receivable balance (in thousands) $ 111,320 $ 151,775 |
Schedule of Percent of Customers by State | December 31, Percent of customers by state Arizona 53 % Nevada 37 % California 10 % |
Schedule of Allowance for Uncollectibles | Activity in the allowance account for uncollectibles is summarized as follows (thousands of dollars): Allowance for Balance, December 31, 2013 $ 1,725 Additions charged to expense 4,146 Accounts written off, less recoveries (3,616 ) Balance, December 31, 2014 2,255 Additions charged to expense 4,113 Accounts written off, less recoveries (4,098 ) Balance, December 31, 2015 2,270 Additions charged to expense 3,264 Accounts written off, less recoveries (3,010 ) Balance, December 31, 2016 $ 2,524 |
Regulatory Assets and Liabili29
Regulatory Assets and Liabilities (Tables) | 12 Months Ended |
Dec. 31, 2016 | |
Regulated Operations [Abstract] | |
Schedule of Regulatory Assets and Liabilities | The following table represents existing regulatory assets and liabilities (thousands of dollars): December 31, 2016 2015 Regulatory assets: Accrued pension and other postretirement benefit costs (1) $ 379,063 $ 384,647 Unrealized net loss on non-trading — 5,486 Deferred purchased gas costs (3) 2,608 3,591 Accrued purchased gas costs (4) 37,100 — Unamortized premium on reacquired debt (5) 21,975 21,511 Accrued absence time (9) 13,440 13,240 Other (6) 23,557 59,782 477,743 488,257 Regulatory liabilities: Deferred purchased gas costs (3) (90,476 ) (45,601 ) Accumulated removal costs (308,000 ) (303,000 ) Accrued purchased gas costs (4) — (10,400 ) Unrealized net gain on non-trading (4,377 ) — Unamortized gain on reacquired debt (7) (9,789 ) (10,325 ) Other (8) (24,659 ) (36,631 ) Net regulatory assets $ 40,442 $ 82,300 (1) Included in Deferred charges and other assets on the Consolidated Balance Sheets. Recovery period is greater than five years. (See Note 10). (2) The following table details the regulatory assets/(liabilities) offsetting the derivatives (Swaps) at fair value in the Consolidated Balance Sheets (thousands of dollars). The actual amounts, when realized at settlement, become a component of purchased gas costs under Southwest’s purchased gas adjustment (“PGA”) mechanisms. (See Note 13). Instrument Balance Sheet Location 2016 2015 Swaps Deferred charges and other assets $ — $ 1,219 Swaps Prepaids and other current assets — 4,267 Swaps Other current liabilities (3,532 ) — Swaps Other deferred credits (845 ) — (3) Balance recovered or refunded on an ongoing basis with interest. (4) Asset included in Prepaids and other current assets and liability included in Other current liabilities on the Consolidated Balance Sheets. Balance recovered or refunded on an ongoing basis. (5) Included in Deferred charges and other assets on the Consolidated Balance Sheets. Recovered over life of debt instruments. (6) The following table details the components of Other regulatory assets which are included in either Prepaids and other current assets or Deferred charges and other assets on the Consolidated Balance Sheets (as indicated). Recovery periods vary. Margin tracking/decoupling mechanisms are alternative revenue programs and revenue associated with under-collections (for the difference between authorized margin levels and amounts billed to customers through rates currently) are recognized as revenue so long as recovery is expected to take place within 24 months. |
Schedule of Components of Other regulatory assets which are included in either Prepaids and other current assets or Deferred charges and other assets on the Consolidated Balance Sheets | Other Regulatory Assets 2016 2015 State mandated public purpose programs (including low income and conservation programs) (a) (f) $ 7,096 $ 18,101 Margin and interest-tracking accounts (b) (f) 3,517 30,339 Infrastructure replacement programs and similar (c) (f) 6,976 6,947 Environmental compliance programs (d) (f) 4,329 2,300 Other (e) 1,639 2,095 $ 23,557 $ 59,782 a) 2016 included in Prepaids and other current assets on the Consolidated Balance Sheets; 2015 included in Deferred charges and other assets on the Consolidated Balance Sheets. b) 2016 included in Prepaids and other current assets on the Consolidated Balance Sheets; 2015 included in Prepaids and other current assets on the Consolidated Balance Sheets ($11 million) and Deferred charges and other assets on the Consolidated Balance Sheets ($19.3 million). c) Included in Deferred charges and other assets on the Consolidated Balance Sheets with the exception of $6,000 in 2016 that is included in Prepaids and other current assets on the Consolidated Balance Sheets. d) 2016 included in Prepaids and other current assets on the Consolidated Balance Sheets ($3.8 million) and Deferred charges and other assets on the Consolidated Balance Sheets ($500,000); 2015 included in Prepaids and other current assets on the Consolidated Balance Sheets ($1.8 million) and Deferred charges and other assets on the Consolidated Balance Sheets ($484,000). e) 2016 included in Prepaids and other current assets on the Consolidated Balance Sheets ($622,000) and Deferred charges and other assets on the Consolidated Balance Sheets ($1 million); 2015 included in Deferred charges and other assets on the Consolidated Balance Sheets. f) Balance recovered or refunded on an ongoing basis, generally with interest. |
Schedule of Components of Other Regulatory Liabilities which are Included in either Other Current Liabilities or Deferred Credits and Other Liabilities on Consolidated Balance Sheets | Other Regulatory Liabilities 2016 2015 State mandated public purpose programs (including low income and conservation programs) (a) (d) $ (7,101 ) $ (4,888 ) Margin and interest-tracking accounts (a) (d) (3,668 ) (20,191 ) Environmental compliance programs (b) (d) (4,469 ) (2,252 ) Regulatory offsets to deferred tax balances (c) (3,390 ) (4,866 ) Regulatory accounts for differences related to pension funding (c) (2,284 ) (1,363 ) Income tax and gross-up (c) (3,203 ) (3,067 ) Other (d) (e) (544 ) (4 ) $ (24,659 ) $ (36,631 ) a) 2016 included in Other current liabilities on the Consolidated Balance Sheets; 2015 included in Other deferred credits and other long-term liabilities on the Consolidated Balance Sheets. b) Included in Other current liabilities on the Consolidated Balance Sheets. c) Included in Other deferred credits and other long-term liabilities on the Consolidated Balance Sheets. d) Balance recovered or refunded on an ongoing basis, generally with interest. e) 2016 included in Other current liabilities on the Consolidated Balance Sheets ($536,000) and in Other deferred credits and other long-term liabilities on the Consolidated Balance Sheets ($8,000); 2015 included in Other deferred credits and other long-term liabilities on the Consolidated Balance Sheets. |
Other Comprehensive Income an30
Other Comprehensive Income and Accumulated Other Comprehensive Income ("AOCI") (Tables) | 12 Months Ended |
Dec. 31, 2016 | |
Equity [Abstract] | |
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) 2016 2015 2014 Before- Tax Amount Tax (Expense) or Net-of- Tax Amount Before- Tax Amount Tax (Expense) or Benefit (1) Net-of- Tax Amount Before- Tax Amount Tax (Expense) or Benefit (1) Net-of- Tax Amount Defined benefit pension plans: Net actuarial gain/(loss) $ (22,770 ) $ 8,652 $ (14,118 ) $ (30,519 ) $ 11,597 $ (18,922 ) $ (173,646 ) $ 65,985 $ (107,661 ) Amortization of prior service cost 1,335 (507 ) 828 1,335 (507 ) 828 355 (135 ) 220 Amortization of net actuarial (gain)/loss 27,066 (10,285 ) 16,781 34,381 (13,065 ) 21,316 23,656 (8,989 ) 14,667 Prior service cost — — — — — — (6,661 ) 2,531 (4,130 ) Regulatory adjustment (5,584 ) 2,122 (3,462 ) (5,646 ) 2,146 (3,500 ) 140,308 (53,317 ) 86,991 Pension plans other comprehensive income (loss) 47 (18 ) 29 (449 ) 171 (278 ) (15,988 ) 6,075 (9,913 ) Forward-starting interest rate swaps (“FSIRS”) (designated hedging activities): Amounts reclassified into net income 3,345 (1,270 ) 2,075 3,344 (1,271 ) 2,073 3,345 (1,272 ) 2,073 FSIRS other comprehensive income (loss) 3,345 (1,270 ) 2,075 3,344 (1,271 ) 2,073 3,345 (1,272 ) 2,073 Foreign currency translation adjustments: Translation adjustments 161 — 161 (1,954 ) — (1,954 ) (659 ) — (659 ) Foreign currency other comprehensive income (loss) 161 — 161 (1,954 ) — (1,954 ) (659 ) — (659 ) Total other comprehensive income (loss) $ 3,553 $ (1,288 ) $ 2,265 $ 941 $ (1,100 ) $ (159 ) $ (13,302 ) $ 4,803 $ (8,499 ) (1) Tax amounts are calculated using a 38% rate. Management has elected to indefinitely reinvest the earnings of Centuri’s Canadian subsidiaries in Canada, thus preventing deferred taxes on such earnings. As a result of this assertion, management is not recognizing any tax effect or presenting a tax expense or benefit for the currency translation adjustment amount reported in Other Comprehensive Income, as repatriation of earnings is not anticipated. |
Schedule of Estimated Amounts Amortized from Accumulated Other Comprehensive Income or Regulatory Assets into Net Periodic Benefit Cost | The estimated amounts that will be amortized from accumulated other comprehensive income or regulatory assets into net periodic benefit cost over the next year are summarized below (in thousands): Retirement plan net actuarial loss $ 24,000 SERP net actuarial loss 1,500 PBOP prior service cost 1,300 |
Rollforward of Accumulated Other Comprehensive Income | The following table represents a rollforward of AOCI, presented on the Company’s Consolidated Balance Sheets and its Consolidated Statements of Equity: AOCI—Rollforward (Thousands of dollars) Defined Benefit Plans (Note 10) FSIRS (Note 13) Foreign Currency Items Before- Tax Tax After- Tax Before- Tax Tax After- Tax Before- Tax Tax After- Tax AOCI Beginning Balance AOCI December 31, 2015 $ (57,660 ) $ 21,911 $ (35,749 ) $ (19,344 ) $ 7,350 $ (11,994 ) $ (2,525 ) $ — $ (2,525 ) $ (50,268 ) Net actuarial gain/(loss) (22,770 ) 8,652 (14,118 ) — — — — — — (14,118 ) Translation adjustments — — — — — — 161 — 161 161 Other comprehensive income before reclassifications (22,770 ) 8,652 (14,118 ) — — — 161 — 161 (13,957 ) FSIRS amounts reclassified from AOCI (1) — — — 3,345 (1,270 ) 2,075 — — — 2,075 Amortization of prior service cost (2) 1,335 (507 ) 828 — — — — — — 828 Amortization of net actuarial loss (2) 27,066 (10,285 ) 16,781 — — — — — — 16,781 Regulatory adjustment (3) (5,584 ) 2,122 (3,462 ) — — — — — — (3,462 ) Net current period other comprehensive income (loss) 47 (18 ) 29 3,345 (1,270 ) 2,075 161 — 161 2,265 Less: Translation adjustment attributable to redeemable noncontrolling interest — — — — — — 5 — 5 5 Net current period other comprehensive income (loss) attributable to Southwest Gas Corporation 47 (18 ) 29 3,345 (1,270 ) 2,075 156 — 156 2,260 Ending Balance AOCI December 31, 2016 $ (57,613 ) $ 21,893 $ (35,720 ) $ (15,999 ) $ 6,080 $ (9,919 ) $ (2,369 ) $ — $ (2,369 ) $ (48,008 ) (1) The FSIRS reclassification amounts are included in the Net interest deductions line item on the Consolidated Statements of Income. (2) These AOCI components are included in the computation of net periodic benefit cost (see Note 10 – Pension and Other Postretirement Benefits (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 Consolidated Balance Sheets). (4) Tax amounts are calculated using a 38% rate. |
Amount Recognized Before Income Tax in Accumulated Other Comprehensive Income | The following table represents amounts (before income tax impacts) included in Accumulated other comprehensive income (in the table above), that have not yet been recognized in net periodic benefit cost as of December 31, 2016 and 2015: Amounts Recognized in AOCI (Before Tax) (Thousands of dollars) 2016 2015 Net actuarial (loss) gain $ (430,973 ) $ (435,269 ) Prior service cost (5,703 ) (7,038 ) Less: amount recognized in regulatory assets 379,063 384,647 Recognized in AOCI $ (57,613 ) $ (57,660 ) |
Long-Term Debt (Tables)
Long-Term Debt (Tables) | 12 Months Ended |
Dec. 31, 2016 | |
Debt Disclosure [Abstract] | |
Schedule of Carrying Amounts and Estimated Fair Values of Long-Term Debt | Since Centuri’s debt is not publicly traded, fair values for the secured revolving credit and term loan facility and other debt obligations were based on a conventional discounted cash flow methodology and utilized current market pricing yield curves, across Centuri’s debt maturity spectrum, of other industrial bonds with an assumed credit rating comparable to the Company’s. December 31, 2016 2015 Carrying Amount Market Value Carrying Amount Market Value (Thousands of dollars) Debentures: Notes, 4.45%, due 2020 $ 125,000 $ 129,703 $ 125,000 $ 130,273 Notes, 6.1%, due 2041 125,000 149,734 125,000 141,581 Notes, 3.875%, due 2022 250,000 254,900 250,000 253,600 Notes, 4.875%, due 2043 250,000 266,793 250,000 251,483 Notes, 3.8%, due 2046 300,000 283,029 — — 8% Series, due 2026 75,000 94,691 75,000 97,035 Medium-term notes, 7.59% series, due 2017 25,000 25,040 25,000 26,253 Medium-term notes, 7.78% series, due 2022 25,000 29,290 25,000 29,855 Medium-term notes, 7.92% series, due 2027 25,000 31,905 25,000 31,890 Medium-term notes, 6.76% series, due 2027 7,500 8,769 7,500 8,684 Unamortized discount and debt issuance costs (9,931 ) (6,137 ) 1,197,569 901,363 Revolving credit facility and commercial paper 5,000 5,000 150,000 150,000 Industrial development revenue bonds: Variable-rate bonds: Tax-exempt 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: 4.85% 2005 Series A, due 2035 — — 100,000 100,452 4.75% 2006 Series A, due 2036 — — 24,855 25,130 Unamortized discount and debt issuance costs (2,489 ) (3,946 ) 197,511 320,909 Centuri term loan facility 106,700 106,819 112,571 112,665 Unamortized debt issuance costs (516 ) (692 ) 106,184 111,879 Centuri secured revolving credit facility 41,185 41,292 60,627 60,724 Centuri other debt obligations 52,635 52,840 25,901 26,059 1,600,084 1,570,679 Less: current maturities (50,101 ) (19,475 ) Long-term debt, less current maturities $ 1,549,983 $ 1,551,204 |
Summary of Effective Interest Rates on Variable-Rate IDRBs | The effective interest rates on Southwest’s variable-rate IDRBs are included in the table below: December 31, December 31, 2003 Series A 1.47 % 0.87 % 2008 Series A 1.53 % 0.87 % 2009 Series A 1.43 % 0.75 % Tax-exempt 1.51 % 0.81 % |
Estimated Maturities of Long-Term Debt | Estimated maturities of long-term debt for the next five years are (in thousands): 2017 $ 50,101 2018 24,082 2019 134,534 2020 134,452 2021 7,815 |
Pension and Other Postretirem32
Pension and Other Postretirement Benefits (Tables) | 12 Months Ended |
Dec. 31, 2016 | |
Compensation and Retirement Disclosure [Abstract] | |
Cost of Retirement Plan | The cost of the plan is disclosed below (in thousands): 2016 2015 2014 Employee Investment Plan cost $ 4,976 $ 5,072 $ 4,816 |
Schedule of Percentage Range of Target Portfolio | At December 31, 2016, the percentage ranges of the target portfolio are: Type of Investment Percentage Range Equity securities 63 to 67 Debt securities 33 to 37 Other up to 1 |
Schedule of Assumptions Used | The rates are presented in the table below: December 31, 2016 December 31, 2015 Discount rate 4.50 % 4.50 % Weighted-average rate of compensation increase 3.25 % 3.25 % Asset return assumption 7.00 % 7.25 % |
Schedule of Amounts Recognized in Balance Sheet and Income Statement | The following table sets forth the retirement plan, SERP, and PBOP funded statuses and amounts recognized on the Consolidated Balance Sheets and Consolidated Statements of Income. 2016 2015 Qualified Retirement Plan SERP PBOP Qualified Retirement Plan SERP PBOP (Thousands of dollars) Change in benefit obligations Benefit obligation for service rendered to date at beginning of year (PBO/PBO/APBO) $ 1,044,817 $ 42,720 $ 72,632 $ 1,060,240 $ 41,176 $ 72,202 Service cost 22,833 331 1,499 25,123 320 1,641 Interest cost 46,027 1,859 3,180 44,229 1,695 2,999 Actuarial loss (gain) 8,550 1,347 (2,060 ) (44,553 ) 2,322 (3,251 ) Benefits paid (73,874 ) (2,946 ) (1,386 ) (40,222 ) (2,793 ) (959 ) Benefit obligation at end of year (PBO/PBO/APBO) 1,048,353 43,311 73,865 1,044,817 42,720 72,632 Change in plan assets Market value of plan assets at beginning of year 736,880 — 43,584 754,796 — 44,892 Actual return on plan assets 39,956 — 4,818 (13,694 ) — (1,034 ) Employer contributions 36,000 2,946 — 36,000 2,793 — Benefits paid (73,874 ) (2,946 ) (289 ) (40,222 ) (2,793 ) (274 ) Market value of plan assets at end of year 738,962 — 48,113 736,880 — 43,584 Funded status at year end $ (309,391 ) $ (43,311 ) $ (25,752 ) $ (307,937 ) $ (42,720 ) $ (29,048 ) Weighted-average assumptions (benefit obligation) Discount rate 4.50 % 4.50 % 4.50 % 4.50 % 4.50 % 4.50 % Weighted-average rate of compensation increase 3.25 % 3.25 % N/A 3.25 % 3.25 % N/A |
Schedule of Accumulated Benefit Obligation | The accumulated benefit obligation for the retirement plan and the SERP is presented below (in thousands): December 31, 2016 December 31, 2015 Retirement plan $ 939,002 $ 922,992 SERP 40,852 39,270 |
Schedule of Expected Benefit Payments | Benefits expected to be paid for pension, SERP, and PBOP over the next 10 years are as follows (in millions): 2017 2018 2019 2020 2021 2022-2026 Pension $ 48.6 $ 50.1 $ 51.5 $ 53.2 $ 55.1 $ 294.2 SERP 2.9 2.9 2.9 2.9 2.9 14.4 PBOP 4.1 4.3 4.4 4.5 4.5 20.6 |
Schedule of Net Periodic Benefit Cost and Weighted-Average Assumptions | Components of net periodic benefit cost Qualified Retirement Plan SERP PBOP 2016 2015 2014 2016 2015 2014 2016 2015 2014 (Thousands of dollars) Service cost $ 22,833 $ 25,123 $ 21,360 $ 331 $ 320 $ 292 $ 1,499 $ 1,641 $ 1,101 Interest cost 46,027 44,229 43,440 1,859 1,695 1,745 3,180 2,999 2,829 Expected return on plan assets (56,558 ) (57,808 ) (53,342 ) — — — (3,149 ) (3,464 ) (3,264 ) Amortization of prior service cost — — — — — — 1,335 1,335 355 Amortization of net actuarial loss 25,266 32,743 22,873 1,383 1,293 783 417 345 — Net periodic benefit cost $ 37,568 $ 44,287 $ 34,331 $ 3,573 $ 3,308 $ 2,820 $ 3,282 $ 2,856 $ 1,021 Weighted-average assumptions (net benefit cost) Discount rate 4.50 % 4.25 % 5.00 % 4.50 % 4.25 % 5.00 % 4.50 % 4.25 % 5.00 % Expected return on plan assets 7.25 % 7.75 % 7.75 % N/A N/A N/A 7.25 % 7.75 % 7.75 % Weighted-average rate of compensation increase 3.25 % 2.75 % 3.25 % 3.25 % 2.75 % 3.25 % N/A N/A N/A |
Schedule of Other Changes in Plan Assets and Benefit Obligations Recognized in Net Periodic Benefit Cost and Other Comprehensive Income | Other Changes in Plan Assets and Benefit Obligations Recognized in Net Periodic Benefit Cost and Other Comprehensive Income 2016 2015 2014 Total Qualified SERP PBOP Total Qualified SERP PBOP Total Qualified SERP PBOP (Thousands of dollars) Net actuarial loss (gain) (a) $ 22,770 $ 25,153 $ 1,347 $ (3,730 ) $ 30,519 $ 26,949 $ 2,322 $ 1,248 $ 173,646 $ 163,215 $ 5,460 $ 4,971 Amortization of prior service cost (b) (1,335 ) — — (1,335 ) (1,335 ) — — (1,335 ) (355 ) — — (355 ) Amortization of net actuarial loss (b) (27,066 ) (25,266 ) (1,383 ) (417 ) (34,381 ) (32,743 ) (1,293 ) (345 ) (23,656 ) (22,872 ) (784 ) — Prior service cost — — — — — — — — 6,661 — — 6,661 Regulatory adjustment 5,584 102 — 5,482 5,646 5,214 — 432 (140,308 ) (129,031 ) — (11,277 ) Recognized in other comprehensive (income) loss (47 ) (11 ) (36 ) — 449 (580 ) 1,029 — 15,988 11,312 4,676 — Net periodic benefit costs recognized in net income 44,423 37,568 3,573 3,282 50,451 44,287 3,308 2,856 38,172 34,331 2,820 1,021 Total of amount recognized in net periodic benefit cost and other comprehensive (income) loss $ 44,376 $ 37,557 $ 3,537 $ 3,282 $ 50,900 $ 43,707 $ 4,337 $ 2,856 $ 54,160 $ 45,643 $ 7,496 $ 1,021 |
Schedule of Fair Value of Plan Assets | The following table sets forth, by level within the three-level fair value hierarchy, the fair values of the assets of the qualified pension plan and the PBOP as of December 31, 2016 and December 31, 2015. The change in the types of pension investment holdings between years is due to the engagement of Russell and the subsequent transition of pension investments to Russell funds. The transition efforts consolidated the majority of the pension plan investments into private commingled equity and fixed income funds. The SERP has no assets. December 31, 2016 December 31, 2015 Qualified PBOP Total Qualified PBOP Total Assets at fair value (thousands of dollars): Level 1 – Quoted prices in active markets for identical financial assets Common stock Agriculture $ — $ — $ — $ 7,021 $ 209 $ 7,230 Capital equipment — — — 533 16 549 Chemicals/materials — — — 3,304 98 3,402 Consumer goods — — — 41,035 1,221 42,256 Energy and mining — — — 11,066 329 11,395 Finance/insurance — — — 29,957 892 30,849 Healthcare — — — 37,930 1,129 39,059 Information technology — — — 29,229 870 30,099 Services — — — 12,341 367 12,708 Telecommunications/internet/media — — — 25,883 770 26,653 Other — — — 9,043 269 9,312 Real estate investment trusts — — — 5,010 149 5,159 Mutual funds — 24,922 24,922 87,483 23,985 111,468 Government fixed income securities — — — 33,482 996 34,478 Futures contracts — — — (7 ) — (7 ) Total Level 1 Assets (1) $ — $ 24,922 $ 24,922 $ 333,310 $ 31,300 $ 364,610 Level 2 – Significant other observable inputs Private commingled equity funds (2) International $ 290,668 $ 9,140 $ 299,808 $ — $ — $ — Large and medium capitalization 121,434 3,819 125,253 — — — Small capitalization 25,947 816 26,763 — — — Emerging markets 45,309 1,424 46,733 — — — Private commingled fixed income funds (3) U.S. corporate bonds 161,086 5,066 166,152 — — — U.S. debt market long duration 77,349 2,432 79,781 — — — U.S. Treasury securities 8,665 272 8,937 — — — Pooled funds and mutual funds 4,889 216 5,105 14,808 796 15,604 Government fixed income and mortgage backed securities 167 5 172 49,571 1,475 51,046 Corporate fixed income securities Asset-backed and mortgage-backed — — — 23,542 701 24,243 Banking — — — 20,857 621 21,478 Insurance — — — 4,896 146 5,042 Utilities — — — 3,826 114 3,940 Other — — — 30,995 922 31,917 Real estate investment trusts — — — 1,949 58 2,007 State and local obligations — — — 950 28 978 Preferred securities — — — 554 17 571 Convertible securities — — — 196 6 202 Total Level 2 assets (4) $ 735,514 $ 23,190 $ 758,704 $ 152,144 $ 4,884 $ 157,028 Total Plan assets at fair value $ 735,514 $ 48,112 $ 783,626 $ 485,454 $ 36,184 $ 521,638 Commingled equity funds (5) — — — 250,511 7,455 257,966 Insurance company general account contracts (6) 3,448 — 3,448 3,719 — 3,719 Total Plan assets (7) $ 738,962 $ 48,112 $ 787,074 $ 739,684 $ 43,639 $ 783,323 (1) The Mutual funds category above is an intermediate-term bond fund whose manager employs multiple concurrent strategies and takes only moderate risk in each, thereby reducing the risk of poor performance arising from any single source, and a balanced fund that invests in a diversified portfolio of common stocks, preferred stocks and fixed-income securities. Strategies utilized by the bond fund include duration management, yield curve or maturity structuring, sector rotation, and all bottom-up in-house In the prior year, Level 1 also included Common stock, Real Estate Investment Trusts, Mutual funds, and U.S. Government securities listed or regularly traded on a national securities exchange and were valued at quoted market prices as of the last business day of the calendar year. (2) The private commingled equity funds include common collective trusts that invest in a diversified portfolio of domestic and international securities regularly traded on securities exchanges. These funds are shown in the above table at net asset value (“NAV”), which is the value of securities in the fund less the amount of any liabilities outstanding. Investment strategies employed by the funds include: • Domestic equities • International developed countries equities • Emerging markets equities Shares in the private equity commingled funds may be redeemed given one business day notice. While they are private equity funds and reported at NAV, due to the short redemption notice period, the lack of significant redemption fees, the fact that the underlying investments are exchange-traded, and that substantial liabilities do not exist subject to the NAV calculation, these investments are viewed as indirectly observable (level 2) and are also therefore, not excluded from the body of the fair value table as a reconciling item. Two funds are classified as international funds. One invests in international financial markets, primarily those of developed economies in Europe and the Pacific Basin. The fund invests primarily in equity securities issued by foreign corporations, but may invest in other securities perceived as offering attractive investment return opportunities. The other provides diversified exposure to global equity markets. The fund seeks to provide long-term capital growth by investing primarily in securities listed on the major developed equity markets of the United States, Europe, and Asia, as well as within those listed on emerging country equity markets on a tactical basis. The large and medium capitalization fund is designed to track the performance of the large and medium capitalization companies contained in the index, which represents approximately 90% of the market capitalization of the United States stock market. The small capitalization fund is designed to provide maximum long-term appreciation through investments that are well diversified by industry. The emerging markets fund was developed to invest in emerging market equities worldwide. The purposes of the fund’s operations, “emerging market countries” include every country in the world except the developed markets of the United States, Canada, Japan, Australia, New Zealand, Hong Kong and Singapore, and most countries located in Western Europe. Fund investments are made directly in each country or, where direct investment is inefficient or prohibited, through appropriate financial instruments or participation in commingled funds. (3) The private commingled fixed income funds include domestic fixed income securities. These funds are shown in the above table at NAV. Shares in the private commingled fixed equity funds may be redeemed given one business day notice. While they are private equity funds and reported at NAV, due to the short redemption notice period, the lack of significant redemption fees, the fact that the underlying investments are exchange-traded, and that substantial liabilities do not exist subject to the NAV calculation, these investments are viewed as indirectly observable (level 2) and are also therefore, not excluded from the body of the fair value table as a reconciling item. The U.S. corporate bond fund seeks to provide high quality, mostly corporate bond-based exposure to fixed income securities which closely match those found in discount curves used to value United States pension liabilities. The United States debt market long duration fund provides participation in the full spectrum of investment opportunities in primarily United States debt markets with longer maturities. The fund seeks to offer effective diversification against equities, take advantage of market trading opportunities, and provide a competitive rate of return on assets. The fund’s current duration is close to 14 years. The United States Treasuries securities funds seeks to replicate the risk and return characteristics of the Barclays Treasury U.S. Separate Trading of Registered Interest and Principal of Securities (“STRIPS”) 28-29 (4) With the exception of items (2) and (3), which are discussed in detail above, the current year Level 2 assets consist mainly of pooled funds and mutual funds. These funds are collective short-term funds that invest in Treasury bills and money market funds and are used as a temporary cash repository. In the prior year, the fair value of the Level 2 investments in debt securities with remaining maturities of one year or more was determined by dealers who make markets in such securities or by an independent pricing service, which considers yield or price of bonds of comparable quality, coupon, maturity, and type. (5) In the prior year, the commingled equity funds included private equity funds that invest in domestic and international securities regularly traded on securities exchanges. These funds are shown in the above table at net asset value, which is the value of securities in the fund less the amount of any liabilities outstanding. Investment strategies employed by the funds included: • Domestic large capitalization value equities • International developed countries value and growth equities • Emerging markets equities • International small capitalization equities The terms and conditions under which shares in the commingled equity funds were redeemed varied among the funds; the notice required ranged from one day to 30 days prior to the valuation date (month end). One of the commingled equity funds required the payment of a minimal impact fee to be applied to redemptions and subscriptions of $5 million or greater; the relative fee diminished the greater the transaction. Other such funds imposed fees to recover direct costs incurred by the fund at redemption, but were indeterminable prior to redemption. (6) The insurance company general account contracts are annuity insurance contracts used to pay the pensions of employees who retired prior to 1989. The balance of the account disclosed in the above table is the contract value, which is the result of deposits, withdrawals, and interest credits. (7) In the prior year, the assets in the above table exceeded the market value of plan assets shown in the funded status table by $2,859,000 (qualified retirement plan – $2,803,000, PBOP – $56,000), which includes a payable for securities purchased, partially offset by receivables for interest, dividends, and securities sold. |
Stock-Based Compensation (Table
Stock-Based Compensation (Tables) | 12 Months Ended |
Dec. 31, 2016 | |
Disclosure of Compensation Related Costs, Share-based Payments [Abstract] | |
Schedule of Stock-Based Plan Compensation Expense, Including Cash Award | The table below shows total stock-based plan compensation expense, including the cash award, which was recognized in the Consolidated Statements of Income (in thousands): 2016 2015 2014 Stock-based compensation plan expense, net of related tax benefits $ 7,185 $ 7,278 $ 8,130 Stock-based compensation plan related tax benefits 4,404 4,461 4,983 |
Schedule of Stock Options Activity | The following tables summarize the stock option plan activity and related information (thousands of options): 2016 2015 2014 Number Weighted- Number of Weighted- Number of Weighted- Outstanding at the beginning of the year 17 $ 31.64 36 $ 28.97 52 $ 27.57 Exercised during the year (17 ) 31.64 (19 ) 26.69 (16 ) 24.31 Forfeited or expired during the year — — — — — — Outstanding and exercisable at year end — N/A 17 $ 31.64 36 $ 28.97 |
Schedule of Aggregate Intrinsic Value of Outstanding and Exercisable Options | The aggregate intrinsic value of outstanding and exercisable options, and options that were exercised, are presented in the table below (in thousands): 2016 2015 2014 Outstanding and exercisable $ — $ 394 $ 1,194 Exercised 554 590 451 |
Summary of Market Prices of Common Stock | December 31, 2016 December 31, 2015 December 31, 2014 Market value of Company stock $ 76.62 $ 55.16 $ 61.81 |
Schedule of Nonvested Performance and Restricted Stock Unit Plans | The following table summarizes the activity of the performance share stock and restricted stock/unit plans as of December 31, 2016 (thousands of shares): Performance Weighted- Restricted Weighted- Nonvested/unissued at beginning of year 197 $ 50.63 228 $ 44.36 Granted 44 59.05 73 60.39 Dividends 5 6 Forfeited or expired — — — — Vested and issued* (78 ) 41.82 (45 ) 51.98 Nonvested/unissued at December 31, 2016 168 $ 55.62 262 $ 46.41 * Includes shares for retiree payouts and those converted for taxes. |
Income Taxes (Tables)
Income Taxes (Tables) | 12 Months Ended |
Dec. 31, 2016 | |
Income Tax Disclosure [Abstract] | |
Summary of Income Before Taxes and Noncontrolling Interest for Domestic and Foreign Operations | The following is a summary of income before taxes and noncontrolling interest for domestic and foreign operations (thousands of dollars): Year ended December 31, 2016 2015 2014 U.S. $ 218,810 $ 221,660 $ 221,471 Foreign 12,713 (2,328 ) (1,950 ) Total income before income taxes $ 231,523 $ 219,332 $ 219,521 |
Summary of Income Tax Expense (Benefit) | Income tax expense (benefit) consists of the following (thousands of dollars): Year Ended December 31, 2016 2015 2014 Current: Federal $ 541 $ 21,321 $ 1,739 State 5,748 9,899 5,073 Foreign 4,298 650 2,193 10,587 31,870 9,005 Deferred: Federal 68,270 51,132 71,439 State 140 (2,574 ) 614 Foreign (529 ) (526 ) (2,685 ) 67,881 48,032 69,368 Total income tax expense $ 78,468 $ 79,902 $ 78,373 |
Significant Components of Deferred Income Tax Expense (Benefit) | Deferred income tax expense (benefit) consists of the following significant components (thousands of dollars): Year Ended December 31, 2016 2015 2014 Deferred federal and state: Property-related items $ 76,217 $ 65,931 $ 52,814 Purchased gas cost adjustments 361 (32,993 ) 15,049 Employee benefits (1,327 ) 623 109 All other deferred (6,532 ) 15,332 2,257 Total deferred federal and state 68,719 48,893 70,229 Deferred ITC, net (838 ) (861 ) (861 ) Total deferred income tax expense $ 67,881 $ 48,032 $ 69,368 |
Reconciliation of U.S Federal Statutory Rate to Consolidated Effective Tax Rate | A reconciliation of the U.S. federal statutory rate to the consolidated effective tax rate for 2014, 2015, and 2016 (and the sources of these differences and the effect of each) are summarized as follows: Year Ended December 31, 2016 2015 2014 U.S. federal statutory income tax rate 35.0 % 35.0 % 35.0 % Net state taxes 1.4 1.8 1.9 Property-related items — 0.1 0.1 Tax credits (0.4 ) (0.4 ) (0.5 ) Company owned life insurance (1.2 ) 0.1 (1.0 ) All other differences (0.9 ) (0.2 ) 0.2 Consolidated effective income tax rate 33.9 % 36.4 % 35.7 % |
Deferred Tax Assets and Liabilities | Deferred tax assets and liabilities consist of the following (thousands of dollars): December 31, 2016 2015 Deferred tax assets: Deferred income taxes for future amortization of ITC $ 1,094 $ 1,614 Employee benefits 38,231 36,923 Alternative minimum tax credit 4,827 4,809 Net operating losses and credits 1,204 868 Interest rate swap 6,080 7,351 Other 18,415 24,636 Valuation allowance (495 ) (499 ) 69,356 75,702 Deferred tax liabilities: Property-related items, including accelerated depreciation 872,136 794,850 Regulatory balancing accounts 1,104 743 Unamortized ITC 1,710 2,549 Debt-related costs 5,712 5,497 Intangibles 8,803 9,547 Other 19,256 31,533 908,721 844,719 Net noncurrent deferred tax liabilities $ 839,365 $ 769,017 |
Reconciliation of Unrecognized Tax Benefits | A reconciliation of the beginning and ending amount of unrecognized tax benefits is as follows (thousands of dollars): 2016 2015 Unrecognized tax benefits at beginning of year $ 296 $ 305 Gross increases – tax positions in prior period 897 — Gross decreases – tax positions in prior period — (9 ) Gross increases – current period tax positions 38 — Gross decreases – current period tax positions — — Settlements — — Lapse in statute of limitations — — Unrecognized tax benefits at end of year $ 1,231 $ 296 |
Derivatives and Fair Value Me35
Derivatives and Fair Value Measurements (Tables) | 12 Months Ended |
Dec. 31, 2016 | |
Fair Value Disclosures [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): December 31, 2016 December 31, 2015 Contract notional amounts 10,543 7,407 |
Amount of Gain or Losses Recognized in Income on Derivatives | The following table sets forth the gains and (losses) recognized on Southwest’s Swaps (derivatives) for the years ended December 31, 2016, 2015, and 2014 and their location in the Consolidated Statements of Income: Gains (losses) recognized in income for derivatives not designated as hedging instruments: (Thousands of dollars) Instrument Location of Gain or (Loss) 2016 2015 2014 Swaps Net cost of gas sold $ 5,006 $ (7,598 ) $ (2,363 ) Swaps Net cost of gas sold (5,006 )* 7,598 * 2,363 * Total $ — $ — $ — * Represents the impact of regulatory deferral accounting treatment under U.S. GAAP for rate-regulated entities. |
Fair Values of Swaps in Consolidated Balance Sheets | The following table sets forth the fair values of the Swaps and their location in the Consolidated Balance Sheets (thousands of dollars): Fair values of derivatives not designated as hedging instruments: December 31, 2016 Instrument Balance Sheet Location Asset Liability Net Swaps Deferred charges and other assets $ 899 $ (54 ) $ 845 Swaps Prepaids and other current assets 3,551 (19 ) 3,532 Total $ 4,450 $ (73 ) $ 4,377 December 31, 2015 Instrument Balance Sheet Location Asset Liability Net Swaps Other current liabilities $ — $ (4,267 ) $ (4,267 ) Swaps Other deferred credits 4 (1,223 ) (1,219 ) Total $ 4 $ (5,490 ) $ (5,486 ) |
Paid to and Received from Counterparties for Settlements of Matured Swaps | The following table presents the amounts paid to and received from counterparties for settlements of matured Swaps. Year ended Year ended Year ended (Thousands of dollars) Paid to counterparties $ 5,583 $ 7,537 $ 829 Received from counterparties $ 726 $ — $ 4,713 |
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 Consolidated Balance Sheets (thousands of dollars). December 31, 2016 Instrument Balance Sheet Location Net Total Swaps Other deferred credits $ (845 ) Swaps Other current liabilities (3,532 ) December 31, 2015 Instrument Balance Sheet Location Net Total Swaps Prepaids and other current assets $ 4,267 Swaps Deferred charges and other assets 1,219 |
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, financial assets and liabilities that were accounted for at fair value (see Note 10 – Pension and Other Post Retirement Benefits for definitions of the levels of the fair value hierarchy): Level 2 – Significant other observable inputs December 31, 2016 December 31, 2015 (Thousands of dollars) Assets at fair value: Prepaids and other current assets – Swaps $ 3,532 $ — Deferred charges and other assets – Swaps 845 — Liabilities at fair value: Other current liabilities – Swaps — (4,267 ) Other deferred credits – Swaps — (1,219 ) Net Assets (Liabilities) $ 4,377 $ (5,486 ) |
Segment Information (Tables)
Segment Information (Tables) | 12 Months Ended |
Dec. 31, 2016 | |
Segment Reporting [Abstract] | |
Accounts Receivable for Services | Accounts receivable for these services, which are not eliminated during consolidation, are presented in the table below (in thousands). December 31, 2016 December 31, 2015 Accounts receivable for Centuri services $ 10,585 $ 10,006 |
Schedule of Revenues by Geographic Area | The following table presents the amount of revenues for both segments by geographic area (thousands of dollars): December 31, December 31, December 31, Revenues (a) United States $ 2,256,600 $ 2,289,133 $ 2,069,513 Canada 203,890 174,492 52,194 Total $ 2,460,490 $ 2,463,625 $ 2,121,707 (a) Revenues are attributed to countries based on the location of customers. |
Schedule of Segment Reporting Information | The financial information pertaining to the natural gas operations and construction services segments for each of the three years in the period ended December 31, 2016 is as follows (thousands of dollars): 2016 Gas Construction Adjustments Total Revenues from unaffiliated customers $ 1,321,412 $ 1,040,957 $ 2,362,369 Intersegment sales — 98,121 98,121 Total $ 1,321,412 $ 1,139,078 $ 2,460,490 Interest revenue $ 1,848 $ 1 $ 1,849 Interest expense $ 66,997 $ 6,663 $ 73,660 Depreciation and amortization $ 233,463 $ 55,669 $ 289,132 Income tax expense $ 58,584 $ 19,884 $ 78,468 Segment net income $ 119,423 $ 32,618 $ 152,041 Segment assets $ 5,001,756 $ 579,370 $ 5,581,126 Capital expenditures $ 457,120 $ 72,411 $ 529,531 2015 Gas Construction Adjustments Total Revenues from unaffiliated customers $ 1,454,639 $ 904,870 $ 2,359,509 Intersegment sales — 104,116 104,116 Total $ 1,454,639 $ 1,008,986 $ 2,463,625 Interest revenue $ 1,754 $ 419 $ 2,173 Interest expense $ 64,095 $ 7,784 $ 71,879 Depreciation and amortization $ 213,455 $ 56,656 $ 270,111 Income tax expense $ 61,355 $ 18,547 $ 79,902 Segment net income $ 111,625 $ 26,692 $ 138,317 Segment assets $ 4,822,845 $ 535,840 $ 5,358,685 Capital expenditures $ 438,289 $ 49,711 $ 488,000 2014 Gas Construction Adjustments (a) Total Revenues from unaffiliated customers $ 1,382,087 $ 647,432 $ 2,029,519 Intersegment sales — 92,188 92,188 Total $ 1,382,087 $ 739,620 $ 2,121,707 Interest revenue $ 2,596 $ 6 $ 2,602 Interest expense $ 68,299 $ 3,770 $ 72,069 Depreciation and amortization $ 204,144 $ 48,883 $ 253,027 Income tax expense $ 63,597 $ 14,776 $ 78,373 Segment net income $ 116,872 $ 24,254 $ 141,126 Segment assets $ 4,652,307 $ 566,589 $ (10,599 ) $ 5,208,297 Capital expenditures $ 350,025 $ 46,873 $ 396,898 (a) Construction services segment assets included two liabilities that were netted against gas operations segment assets during consolidation in 2014. They are: Income taxes payable of $3.3 million, netted against income taxes receivable, net and deferred income taxes of $1.4 million, netted against deferred income taxes, net. Construction services segment assets exclude a long-term deferred tax benefit of $1.4 million, which was netted against gas operations segment deferred income taxes and investment tax credits, net during consolidation. Gas operations segment assets include a deferred income tax liability of $4.5 million, which was netted against a construction services segment asset for deferred income taxes, net during consolidation. |
Quarterly Financial Data (Table
Quarterly Financial Data (Tables) | 12 Months Ended |
Dec. 31, 2016 | |
Quarterly Financial Information Disclosure [Abstract] | |
Schedule of Quarterly Financial Information | Quarter Ended March 31 June 30 September 30 December 31 (Thousands of dollars, except per share amounts) 2016 Operating revenues $ 731,248 $ 547,748 $ 539,969 $ 641,525 Operating income 134,096 28,116 15,539 117,963 Net income 75,355 9,099 2,907 65,694 Net income attributable to Southwest Gas Corporation 75,446 8,943 2,472 65,180 Basic earnings per common share* 1.59 0.19 0.05 1.37 Diluted earnings per common share* 1.58 0.19 0.05 1.36 2015 Operating revenues $ 734,220 $ 538,604 $ 505,396 $ 685,405 Operating income 129,556 25,047 16,143 117,586 Net income (loss) 71,879 5,063 (4,210 ) 66,698 Net income (loss) attributable to Southwest Gas Corporation 71,983 4,949 (4,734 ) 66,119 Basic earnings (loss) per common share* 1.54 0.11 (0.10 ) 1.40 Diluted earnings (loss) per common share* 1.53 0.10 (0.10 ) 1.38 2014 Operating revenues $ 608,396 $ 453,153 $ 432,475 $ 627,683 Operating income 127,065 26,755 18,290 112,373 Net income 70,697 9,627 1,927 58,897 Net income attributable to Southwest Gas Corporation 70,783 9,627 1,970 58,746 Basic earnings per common share* 1.52 0.21 0.04 1.26 Diluted earnings per common share* 1.51 0.21 0.04 1.25 * The sum of quarterly earnings (loss) per average common share may not equal the annual earnings (loss) per share due to the ongoing change in the weighted-average number of common shares outstanding. |
Construction Services Noncont38
Construction Services Noncontrolling Interests (Tables) | 12 Months Ended |
Dec. 31, 2016 | |
Noncontrolling Interest [Abstract] | |
Summary of Redeemable Noncontrolling Interest | The following depicts impacts to the balance of the redeemable noncontrolling interest between the indicated periods. Redeemable (Thousands of dollars): Balance, December 31, 2015 $ 16,108 Net Income (loss) attributable to redeemable noncontrolling interest 1,148 Foreign currency exchange translation adjustment 5 Centuri distribution to redeemable noncontrolling interest (439 ) Adjustment to redemption value 5,768 Balance, December 31, 2016 $ 22,590 |
Summary of Significant Accoun39
Summary of Significant Accounting Policies - Additional Information (Detail) | May 06, 2016USD ($) | Dec. 31, 2016USD ($)SegmentMarkets | Dec. 31, 2015USD ($) | Dec. 31, 2014USD ($) |
Significant Accounting Policies [Line Items] | ||||
Number of segments | Segment | 2 | |||
Earnings from equity method investment | $ 69,000 | $ 310,000 | $ 107,000 | |
Non-cash construction advances - non-cash investing item | 6,500,000 | 3,100,000 | 8,100,000 | |
Non-cash investing outflow activity | 10,800,000 | |||
Goodwill impairment charges | 0 | 0 | ||
Purchase price paid in cash | $ 17,000,000 | |||
Business acquisition deferred payment period | 4 years | |||
Reduction in depreciation expense due to extension of estimates useful lives | $ 4,000,000 | |||
Non-controlling Interest [Member] | ||||
Significant Accounting Policies [Line Items] | ||||
Non-cash investing outflow activity | $ 18,900,000 | |||
IntelliChoice Energy, LLC [Member] | ||||
Significant Accounting Policies [Line Items] | ||||
Subsidiaries holding interest percentage | 65.00% | |||
W.S. Nicholls Western Construction LTD. [Member] | ||||
Significant Accounting Policies [Line Items] | ||||
Investment amount | $ 10,800,000 | 10,800,000 | ||
Dividends | 500,000 | |||
Exposure to loss as a result of its investment | 35,800,000 | |||
Earnings from equity method investment | $ 69,000 | |||
Matheson-Nicholls Joint Venture [Member] | ||||
Significant Accounting Policies [Line Items] | ||||
Subsidiaries holding interest percentage | 50.00% | |||
CCI-TBN Toronto, Inc [Member] | ||||
Significant Accounting Policies [Line Items] | ||||
Subsidiaries holding interest percentage | 25.00% | |||
Centuri Construction Group Inc [Member] | ||||
Significant Accounting Policies [Line Items] | ||||
Ownership percentage in subsidiary | 96.60% | |||
Intangible assets | $ 37,669,000 | 36,773,000 | ||
Centuri Construction Group Inc [Member] | W.S. Nicholls Western Construction LTD. [Member] | ||||
Significant Accounting Policies [Line Items] | ||||
Subsidiaries holding interest percentage | 50.00% | |||
Pooled Funds and Mutual Funds [Member] | Level 2 - Significant Other Observable Inputs [Member] | ||||
Significant Accounting Policies [Line Items] | ||||
Money market fund investments | $ 5,300,000 | 250,000 | ||
United States [Member] | Centuri Construction Group Inc [Member] | ||||
Significant Accounting Policies [Line Items] | ||||
Number of major markets in the United States | Markets | 20 | |||
Gas Pipe Materials and Supplies [Member] | ||||
Significant Accounting Policies [Line Items] | ||||
Gas pipe materials and operating supplies | $ 30,000,000 | $ 24,000,000 | ||
Foreign Jurisdiction [Member] | ||||
Significant Accounting Policies [Line Items] | ||||
Cumulative earnings | $ 5,000,000 |
Summary of Significant Accoun40
Summary of Significant Accounting Policies - Schedule of Other Property and Investments (Detail) - USD ($) $ in Thousands | Dec. 31, 2016 | Dec. 31, 2015 |
Investment [Line Items] | ||
Net cash surrender value of COLI policies | $ 106,744,000 | $ 99,276,000 |
Other property | 12,859,000 | 11,914,000 |
Total | 342,343 | 313,531 |
Centuri Construction Group Inc [Member] | ||
Investment [Line Items] | ||
Centuri property, equipment, and intangibles | 451,114,000 | 423,369,000 |
Centuri accumulated provision for depreciation and amortization | $ (228,374,000) | $ (221,028,000) |
Summary of Significant Accoun41
Summary of Significant Accounting Policies - Schedule of Goodwill (Detail) $ in Thousands | 12 Months Ended |
Dec. 31, 2016USD ($) | |
Goodwill [Line Items] | |
Goodwill, Beginning balance | $ 126,145 |
Foreign currency translation adjustment | 3,112 |
Goodwill, Ending balance | 139,983 |
ETTI [Member] | |
Goodwill [Line Items] | |
Additional goodwill from ETTI acquisition | 10,726 |
Natural Gas Operations [Member] | |
Goodwill [Line Items] | |
Goodwill, Beginning balance | 10,095 |
Foreign currency translation adjustment | 0 |
Goodwill, Ending balance | 10,095 |
Natural Gas Operations [Member] | ETTI [Member] | |
Goodwill [Line Items] | |
Additional goodwill from ETTI acquisition | 0 |
Construction Services [Member] | |
Goodwill [Line Items] | |
Goodwill, Beginning balance | 116,050 |
Foreign currency translation adjustment | 3,112 |
Goodwill, Ending balance | 129,888 |
Construction Services [Member] | ETTI [Member] | |
Goodwill [Line Items] | |
Additional goodwill from ETTI acquisition | $ 10,726 |
Summary of Significant Accoun42
Summary of Significant Accounting Policies - Estimated Fair Values of Assets Acquired as of Acquisition Date (Detail) - USD ($) $ in Thousands | Dec. 31, 2016 | May 06, 2016 | Dec. 31, 2015 |
Business Acquisition [Line Items] | |||
Goodwill | $ 139,983 | $ 126,145 | |
ETTI [Member] | |||
Business Acquisition [Line Items] | |||
Property, plant and equipment | $ 4,300 | ||
Intangible assets | 2,900 | ||
Goodwill | 10,700 | ||
Total assets acquired | $ 17,900 |
Summary of Significant Accoun43
Summary of Significant Accounting Policies - Summary of Intangible Assets (Detail) - Centuri Construction Group Inc [Member] - USD ($) $ in Thousands | Dec. 31, 2016 | Dec. 31, 2015 |
Finite-Lived Intangible Assets [Line Items] | ||
Gross Carrying Amount | $ 46,067 | $ 41,890 |
Accumulated Amortization | (8,398) | (5,117) |
Net Carrying Amount | 37,669 | 36,773 |
Customer Relationships [Member] | ||
Finite-Lived Intangible Assets [Line Items] | ||
Gross Carrying Amount | 34,033 | 31,226 |
Accumulated Amortization | (3,906) | (2,070) |
Net Carrying Amount | 30,127 | 29,156 |
Trade Names and Trademarks [Member] | ||
Finite-Lived Intangible Assets [Line Items] | ||
Gross Carrying Amount | 9,349 | 8,621 |
Accumulated Amortization | (2,565) | (1,331) |
Net Carrying Amount | 6,784 | 7,290 |
Customer Contracts Backlog [Member] | ||
Finite-Lived Intangible Assets [Line Items] | ||
Gross Carrying Amount | 1,656 | 1,606 |
Accumulated Amortization | (1,656) | (1,606) |
Net Carrying Amount | 0 | 0 |
Noncompete Agreement [Member] | ||
Finite-Lived Intangible Assets [Line Items] | ||
Gross Carrying Amount | 1,029 | 437 |
Accumulated Amortization | (271) | (110) |
Net Carrying Amount | $ 758 | $ 327 |
Summary of Significant Accoun44
Summary of Significant Accounting Policies - Schedule of Estimated Future Amortization of Intangible Assets (Detail) $ in Thousands | Dec. 31, 2016USD ($) |
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract] | |
2,017 | $ 3,339 |
2,018 | 3,126 |
2,019 | 2,463 |
2,020 | 2,395 |
2,021 | $ 2,269 |
Summary of Significant Accoun45
Summary of Significant Accounting Policies - Schedule of Capitalized and Debt Portion of AFUDC (Detail) - USD ($) $ in Thousands | 12 Months Ended | ||
Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2014 | |
Public Utilities, Allowance for Funds Used During Construction, Net Increase [Abstract] | |||
Debt portion | $ 1,175 | $ 1,666 | $ 1,228 |
Equity portion | 2,289 | 3,008 | 1,995 |
AFUDC capitalized as part of utility plant | $ 3,464 | $ 4,674 | $ 3,223 |
AFUDC rate | 7.35% | 7.32% | 7.73% |
Summary of Significant Accoun46
Summary of Significant Accounting Policies - Other Income (Deductions) (Detail) - USD ($) $ in Thousands | 12 Months Ended | ||
Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2014 | |
Other Income and Expenses [Abstract] | |||
Change in COLI policies | $ 7,400 | $ (500) | $ 5,300 |
Interest income | 1,849 | 2,173 | 2,602 |
Equity AFUDC | 2,289 | 3,008 | 1,995 |
Foreign currency transaction gain (loss) | (22) | (824) | (178) |
Equity in earnings of unconsolidated investment - Western | 69 | 310 | 107 |
Miscellaneous income and (expense) | (2,116) | (1,288) | (2,719) |
Total other income (deductions) | $ 9,469 | $ 2,879 | $ 7,107 |
Summary of Significant Accoun47
Summary of Significant Accounting Policies - Schedule of Earnings Per Share, Basic and Diluted (Detail) - shares shares in Thousands | 12 Months Ended | ||
Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2014 | |
Weighted Average Number of Shares Outstanding, Diluted [Abstract] | |||
Average basic shares | 47,469 | 46,992 | 46,494 |
Stock options | 1 | 8 | 17 |
Performance shares | 124 | 171 | 215 |
Restricted stock units | 220 | 212 | 218 |
Average diluted shares | 47,814 | 47,383 | 46,944 |
Utility Plant and Leases - Sche
Utility Plant and Leases - Schedule of Net Utility Plant (Detail) - USD ($) $ in Thousands | Dec. 31, 2016 | Dec. 31, 2015 |
Public Utility, Property, Plant and Equipment [Line Items] | ||
Gas plant | $ 6,193,564 | $ 5,854,917 |
Less: accumulated depreciation | (2,172,966) | (2,084,007) |
Acquisition adjustments, net | 196 | 370 |
Construction work in progress | 111,177 | 119,805 |
Net utility plant | 4,131,971 | 3,891,085 |
Software and Software-related Intangibles [Member] | ||
Public Utility, Property, Plant and Equipment [Line Items] | ||
Gas plant | 224,260 | 203,323 |
Storage [Member] | ||
Public Utility, Property, Plant and Equipment [Line Items] | ||
Gas plant | 24,614 | 22,944 |
Transmission [Member] | ||
Public Utility, Property, Plant and Equipment [Line Items] | ||
Gas plant | 349,981 | 312,996 |
Distribution [Member] | ||
Public Utility, Property, Plant and Equipment [Line Items] | ||
Gas plant | 5,198,531 | 4,935,730 |
General [Member] | ||
Public Utility, Property, Plant and Equipment [Line Items] | ||
Gas plant | 382,084 | 365,865 |
Other [Member] | ||
Public Utility, Property, Plant and Equipment [Line Items] | ||
Gas plant | $ 14,094 | $ 14,059 |
Utility Plant and Leases - Addi
Utility Plant and Leases - Additional Information (Detail) - USD ($) $ in Millions | 12 Months Ended | ||
Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2014 | |
Public Utility, Property, Plant and Equipment [Line Items] | |||
Annual depreciation and amortization expense percentage | 3.60% | 3.60% | 3.60% |
Gas, Transmission and Distribution Plant [Member] | |||
Public Utility, Property, Plant and Equipment [Line Items] | |||
Annual depreciation and amortization expense percentage | 3.30% | 3.30% | 3.30% |
Gas plant [Member] | |||
Public Utility, Property, Plant and Equipment [Line Items] | |||
Amortization of intangibles | $ 14.8 | $ 12.7 | $ 11.7 |
Utility Plant and Leases - Sc50
Utility Plant and Leases - Schedule of Depreciation and Amortization Expense (Detail) - USD ($) $ in Thousands | 12 Months Ended | ||
Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2014 | |
Public Utility, Property, Plant and Equipment [Line Items] | |||
Depreciation and amortization expense | $ 289,132 | $ 270,111 | $ 253,027 |
Gas plant [Member] | |||
Public Utility, Property, Plant and Equipment [Line Items] | |||
Depreciation and amortization expense | $ 214,037 | $ 201,233 | $ 194,360 |
Utility Plant and Leases - Sc51
Utility Plant and Leases - Schedule of Rental Payments for Operating Leases (Detail) - USD ($) $ in Thousands | 12 Months Ended | ||
Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2014 | |
Rental Payments And Lease Payments Included In Operating Expenses [Line Items] | |||
Consolidated rental payments/lease expense | $ 58,313 | $ 50,035 | $ 35,342 |
Southwest Gas [Member] | |||
Rental Payments And Lease Payments Included In Operating Expenses [Line Items] | |||
Consolidated rental payments/lease expense | 4,357 | 4,186 | 5,330 |
Centuri Construction Group Inc [Member] | |||
Rental Payments And Lease Payments Included In Operating Expenses [Line Items] | |||
Consolidated rental payments/lease expense | $ 53,956 | $ 45,849 | $ 30,012 |
Utility Plant and Leases - Sc52
Utility Plant and Leases - Schedule of Future Minimum Lease Payments for Operating Leases (Detail) $ in Thousands | Dec. 31, 2016USD ($) |
Leases [Abstract] | |
2,017 | $ 6,929 |
2,018 | 4,837 |
2,019 | 3,449 |
2,020 | 2,411 |
2,021 | 1,098 |
Thereafter | 2,730 |
Total minimum lease payments | $ 21,454 |
Utility Plant and Leases - Sc53
Utility Plant and Leases - Schedule of Capital Leases of Equipment (Detail) - USD ($) $ in Thousands | Dec. 31, 2016 | Dec. 31, 2015 |
Leases [Abstract] | ||
Capital leased assets, gross | $ 3,189 | $ 4,584 |
Less: accumulated amortization | (1,172) | (1,043) |
Capital leased assets, net | $ 2,017 | $ 3,541 |
Utility Plant and Leases - Sc54
Utility Plant and Leases - Schedule of Future Minimum Lease Payments for Capital Leases (Detail) $ in Thousands | Dec. 31, 2016USD ($) |
Leases [Abstract] | |
2,017 | $ 931 |
2,018 | 546 |
2,019 | 84 |
2,020 | 0 |
2,021 | 0 |
Thereafter | 0 |
Future minimum lease payments due | 1,561 |
Less: amount representing interest | (101) |
Total minimum lease payments | $ 1,460 |
Receivables and Related Allow55
Receivables and Related Allowances - Schedule of Accounts Receivable (Detail) - USD ($) $ in Thousands | 12 Months Ended | |
Dec. 31, 2016 | Dec. 31, 2015 | |
Receivables [Abstract] | ||
Gas utility customer accounts receivable balance | $ 111,320 | $ 151,775 |
Receivables and Related Allow56
Receivables and Related Allowances - Schedule of Percent of Customers by State (Detail) | 12 Months Ended |
Dec. 31, 2016 | |
Arizona [Member] | |
Receivables And Related Allowances [Line Items] | |
Percent of customers by state | 53.00% |
Nevada [Member] | |
Receivables And Related Allowances [Line Items] | |
Percent of customers by state | 37.00% |
California [Member] | |
Receivables And Related Allowances [Line Items] | |
Percent of customers by state | 10.00% |
Receivables and Related Allow57
Receivables and Related Allowances - Schedule of Allowance for Uncollectibles (Detail) - Allowance for Uncollectibles [Member] - USD ($) $ in Thousands | 12 Months Ended | ||
Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2014 | |
Receivables And Related Allowances [Line Items] | |||
Beginning Balance | $ 2,270 | $ 2,255 | $ 1,725 |
Additions charged to expense | 3,264 | 4,113 | 4,146 |
Accounts written off, less recoveries | (3,010) | (4,098) | (3,616) |
Ending Balance | $ 2,524 | $ 2,270 | $ 2,255 |
Receivables and Related Allow58
Receivables and Related Allowances - Additional Information (Detail) - USD ($) $ in Thousands | Dec. 31, 2016 | Dec. 31, 2015 |
Receivables And Related Allowances [Line Items] | ||
Customer accounts receivable | $ 285,145 | $ 314,512 |
Centuri Construction Group Inc [Member] | ||
Receivables And Related Allowances [Line Items] | ||
Customer accounts receivable | $ 173,000 |
Regulatory Assets and Liabili59
Regulatory Assets and Liabilities - Schedule of Regulatory Assets and Liabilities (Detail) - USD ($) $ in Thousands | Dec. 31, 2016 | Dec. 31, 2015 |
Regulatory Assets And Liabilities [Line Items] | ||
Regulatory assets, total | $ 477,743 | $ 488,257 |
Net regulatory assets | 40,442 | 82,300 |
Regulatory liabilities, total | (24,659) | (36,631) |
Accrued Pension and Other Postretirement Benefit Costs [Member] | ||
Regulatory Assets And Liabilities [Line Items] | ||
Regulatory assets, total | 379,063 | 384,647 |
Unrealized Net Loss on Non-trading Derivatives (Swaps) [Member] | ||
Regulatory Assets And Liabilities [Line Items] | ||
Regulatory assets, total | 0 | 5,486 |
Regulatory liabilities, total | (4,377) | 0 |
Deferred Purchased Gas Costs [Member] | ||
Regulatory Assets And Liabilities [Line Items] | ||
Regulatory assets, total | 2,608 | 3,591 |
Regulatory liabilities, total | (90,476) | (45,601) |
Accrued Purchased Gas Costs [Member] | ||
Regulatory Assets And Liabilities [Line Items] | ||
Regulatory assets, total | 37,100 | 0 |
Regulatory liabilities, total | 0 | (10,400) |
Unamortized Premium on Reacquired Debt [Member] | ||
Regulatory Assets And Liabilities [Line Items] | ||
Regulatory assets, total | 21,975 | 21,511 |
Accrued Absence Time [Member] | ||
Regulatory Assets And Liabilities [Line Items] | ||
Regulatory assets, total | 13,440 | 13,240 |
Other [Member] | ||
Regulatory Assets And Liabilities [Line Items] | ||
Regulatory assets, total | 23,557 | 59,782 |
Accumulated Removal Costs [Member] | ||
Regulatory Assets And Liabilities [Line Items] | ||
Regulatory liabilities, total | (308,000) | (303,000) |
Unamortized Gain on Reacquired Debt [Member] | ||
Regulatory Assets And Liabilities [Line Items] | ||
Regulatory liabilities, total | (9,789) | (10,325) |
Other [Member] | ||
Regulatory Assets And Liabilities [Line Items] | ||
Regulatory liabilities, total | $ (24,659) | $ (36,631) |
Regulatory Assets and Liabili60
Regulatory Assets and Liabilities - Schedule of Regulatory Assets and Liabilities (Parenthetical) (Detail) - Swaps [Member] - USD ($) $ in Thousands | Dec. 31, 2016 | Dec. 31, 2015 |
Deferred Charges and Other Assets [Member] | ||
Regulatory Assets And Liabilities [Line Items] | ||
Regulatory assets and liabilities offsetting derivatives at fair value | $ 0 | $ 1,219 |
Prepaids and Other Current Assets [Member] | ||
Regulatory Assets And Liabilities [Line Items] | ||
Regulatory assets and liabilities offsetting derivatives at fair value | 0 | 4,267 |
Other Current Liabilities [Member] | ||
Regulatory Assets And Liabilities [Line Items] | ||
Regulatory assets and liabilities offsetting derivatives at fair value | (3,532) | 0 |
Other Deferred Credits [Member] | ||
Regulatory Assets And Liabilities [Line Items] | ||
Regulatory assets and liabilities offsetting derivatives at fair value | $ (845) | $ 0 |
Regulatory Assets and Liabili61
Regulatory Assets and Liabilities - Schedule of Components of Other Regulatory Assets are Included in either Prepaids and Other Current Assets or Deferred Credits and Other Assets on the Consolidated Balance Sheets (Detail) - USD ($) $ in Thousands | Dec. 31, 2016 | Dec. 31, 2015 |
Regulatory Assets [Line Items] | ||
Regulatory assets | $ 477,743 | $ 488,257 |
State Mandate Public Purpose Programs (Including Low Income and Conservation Programs) [Member] | ||
Regulatory Assets [Line Items] | ||
Regulatory assets | 7,096 | 18,101 |
Margin and Interest-Tracking Accounts [Member] | ||
Regulatory Assets [Line Items] | ||
Regulatory assets | 3,517 | 30,339 |
Infrastructure Replacement Programs and Similar [Member] | ||
Regulatory Assets [Line Items] | ||
Regulatory assets | 6,976 | 6,947 |
Environmental Compliance Programs [Member] | ||
Regulatory Assets [Line Items] | ||
Regulatory assets | 4,329 | 2,300 |
Other [Member] | ||
Regulatory Assets [Line Items] | ||
Regulatory assets | 1,639 | 2,095 |
Other Regulatory Assets [Member] | ||
Regulatory Assets [Line Items] | ||
Regulatory assets | $ 23,557 | $ 59,782 |
Regulatory Assets and Liabili62
Regulatory Assets and Liabilities - Schedule of Components of Other Regulatory Assets are Included in Deferred Credits and Other Assets on the Consolidated Balance Sheets (Parenthetical) (Detail) - USD ($) $ in Thousands | Dec. 31, 2016 | Dec. 31, 2015 |
Regulatory Assets [Line Items] | ||
Prepaid and other current assets | $ 136,833 | $ 95,199 |
Deferred charges and other assets | 432,234 | 469,322 |
Margin and Interest-Tracking Accounts [Member] | ||
Regulatory Assets [Line Items] | ||
Prepaid and other current assets | 11,000 | |
Deferred charges and other assets | 19,300 | |
Infrastructure Replacement Programs and Similar [Member] | ||
Regulatory Assets [Line Items] | ||
Prepaid and other current assets | 6,000 | |
Environmental Compliance Programs [Member] | ||
Regulatory Assets [Line Items] | ||
Prepaid and other current assets | 3,800 | 1,800 |
Deferred charges and other assets | 500,000 | $ 484,000 |
Other Regulatory Assets [Member] | ||
Regulatory Assets [Line Items] | ||
Prepaid and other current assets | 622,000 | |
Deferred charges and other assets | $ 1,000 |
Regulatory Assets and Liabili63
Regulatory Assets and Liabilities - Schedule of Components of Other Regulatory Liabilities are Included in either Other Current Liabilities or Deferred Credits and Other Liabilities on Consolidated Balance Sheets (Detail) - USD ($) $ in Thousands | Dec. 31, 2016 | Dec. 31, 2015 |
Regulatory Liabilities [Line Items] | ||
Regulatory liabilities | $ (24,659) | $ (36,631) |
State Mandate Public Purpose Programs (Including Low Income and Conservation Programs) [Member] | ||
Regulatory Liabilities [Line Items] | ||
Regulatory liabilities | (7,101) | (4,888) |
Margin and Interest-Tracking Accounts [Member] | ||
Regulatory Liabilities [Line Items] | ||
Regulatory liabilities | (3,668) | (20,191) |
Environmental Compliance Programs [Member] | ||
Regulatory Liabilities [Line Items] | ||
Regulatory liabilities | (4,469) | (2,252) |
Regulatory Offsets To Deferred Tax Balances [Member] | ||
Regulatory Liabilities [Line Items] | ||
Regulatory liabilities | (3,390) | (4,866) |
Regulatory Accounts for Differences Related to Pension Funding [Member] | ||
Regulatory Liabilities [Line Items] | ||
Regulatory liabilities | (2,284) | (1,363) |
Income Tax and Gross-Up [Member] | ||
Regulatory Liabilities [Line Items] | ||
Regulatory liabilities | (3,203) | (3,067) |
Other Regulatory Liabilities [Member] | ||
Regulatory Liabilities [Line Items] | ||
Regulatory liabilities | $ (544) | $ (4) |
Regulatory Assets and Liabili64
Regulatory Assets and Liabilities - Schedule of Components of Other Regulatory Liabilities are Included in either Other Current Liabilities or Deferred Credits and Other Liabilities on Consolidated Balance Sheets (Parenthetical) (Detail) - USD ($) | Dec. 31, 2016 | Dec. 31, 2015 |
Regulatory Liabilities [Line Items] | ||
Other current liabilities | $ 168,064,000 | $ 150,031,000 |
Other deferred credits and other long-term liabilities | 570,252,000 | $ 591,558,000 |
Other Regulatory Liabilities [Member] | ||
Regulatory Liabilities [Line Items] | ||
Other current liabilities | 536,000 | |
Other deferred credits and other long-term liabilities | $ 8,000 |
Other Comprehensive Income an65
Other Comprehensive Income and Accumulated Other Comprehensive Income ("AOCI") - Related Tax Effects Allocated to Each Component of Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Thousands | 12 Months Ended | ||
Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2014 | |
Equity [Abstract] | |||
Net actuarial gain/(loss), Before-Tax Amount | $ (22,770) | $ (30,519) | $ (173,646) |
Amortization of prior service cost, Before-Tax Amount | 1,335 | 1,335 | 355 |
Amortization of net actuarial (gain)/loss, Before-Tax Amount | 27,066 | 34,381 | 23,656 |
Prior service cost, Before-Tax Amount | 0 | 0 | (6,661) |
Regulatory adjustment, Before-Tax Amount | (5,584) | (5,646) | 140,308 |
Net current period other comprehensive income (loss), Defined Benefit Plans Before-Tax | 47 | (449) | (15,988) |
Amounts reclassified into net income, Before-Tax Amount | 3,345 | 3,344 | 3,345 |
FSIRS other comprehensive income (loss), Before-Tax Amount | 3,345 | 3,344 | 3,345 |
Translation adjustments, Before-Tax Amount | 161 | (1,954) | (659) |
Foreign currency other comprehensive income (loss), Before-Tax Amount | 161 | (1,954) | (659) |
Total other comprehensive income (loss), Before-Tax Amount | 3,553 | 941 | (13,302) |
Net actuarial gain/(loss), Tax (Expense) or Benefit | 8,652 | 11,597 | 65,985 |
Amortization of prior service cost, Tax (Expense) or Benefit | (507) | (507) | (135) |
Amortization of net actuarial (gain)/loss, Tax (Expense) or Benefit | (10,285) | (13,065) | (8,989) |
Prior service cost, Tax (Expense) or Benefit | 0 | 0 | 2,531 |
Regulatory adjustment, Tax (Expense) or Benefit | 2,122 | 2,146 | (53,317) |
Pension plans other comprehensive income (loss), Tax (Expense) or Benefit | (18) | 171 | 6,075 |
Amounts reclassified into net income, Tax (Expense) or Benefit | (1,270) | (1,271) | (1,272) |
FSIRS other comprehensive income (loss), Tax (Expense) or Benefit | (1,270) | (1,271) | (1,272) |
Translation adjustments, Tax (Expense) or Benefit | 0 | 0 | 0 |
Foreign currency other comprehensive income (loss), Tax (Expense) or Benefit | 0 | 0 | 0 |
Total other comprehensive income (loss), Tax (Expense) or Benefit | (1,288) | (1,100) | 4,803 |
Net actuarial gain/(loss), Net-of-Tax Amount | (14,118) | (18,922) | (107,661) |
Amortization of prior service cost, Net-of-Tax Amount | 828 | 828 | 220 |
Amortization of net actuarial (gain)/loss, Defined Benefit Plans After-Tax | 16,781 | 21,316 | 14,667 |
Prior service cost, Net-of-Tax Amount | 0 | 0 | (4,130) |
Regulatory adjustment, Net-of-Tax Amount | (3,462) | (3,500) | 86,991 |
Pension plans other comprehensive income (loss), Net-of-Tax Amount | 29 | (278) | (9,913) |
Amounts reclassified into net income (Notes 5 and 13) | 2,075 | 2,073 | 2,073 |
FSIRS other comprehensive income (loss), Net-of-Tax Amount | 2,075 | 2,073 | 2,073 |
Translation adjustments, Net-of-Tax Amount | 161 | (1,954) | (659) |
Foreign currency other comprehensive income (loss), Net-of-Tax Amount | 161 | (1,954) | (659) |
Total other comprehensive income (loss), net of tax | $ 2,265 | $ (159) | $ (8,499) |
Other Comprehensive Income an66
Other Comprehensive Income and Accumulated Other Comprehensive Income ("AOCI") - Related Tax Effects Allocated to Each Component of Other Comprehensive Income (Loss) (Parenthetical) (Detail) | 12 Months Ended |
Dec. 31, 2016USD ($) | |
Equity [Abstract] | |
Other comprehensive income loss, effective income tax rate | 38.00% |
Tax expense or benefit for currency translation adjustment | $ 0 |
Other Comprehensive Income an67
Other Comprehensive Income and Accumulated Other Comprehensive Income ("AOCI") - Schedule of Estimated Amounts Amortized from Accumulated Other Comprehensive Income or Regulatory Assets into Net Periodic Benefit Cost (Detail) $ in Thousands | 12 Months Ended |
Dec. 31, 2016USD ($) | |
Qualified Retirement Plan [Member] | |
Defined Benefit Plan Disclosure [Line Items] | |
Retirement plan net actuarial loss | $ 24,000 |
SERP [Member] | |
Defined Benefit Plan Disclosure [Line Items] | |
Retirement plan net actuarial loss | 1,500 |
PBOP [Member] | |
Defined Benefit Plan Disclosure [Line Items] | |
PBOP prior service cost | $ 1,300 |
Other Comprehensive Income an68
Other Comprehensive Income and Accumulated Other Comprehensive Income ("AOCI") - Additional Information (Detail) $ in Millions | Dec. 31, 2016USD ($) |
Equity [Abstract] | |
Amount of FSIRS existing AOCI losses expected to reclassified income in next twelve months | $ 2.1 |
Other Comprehensive Income an69
Other Comprehensive Income and Accumulated Other Comprehensive Income ("AOCI") - Rollforward of Accumulated Other Comprehensive Income (Detail) - USD ($) $ in Thousands | 12 Months Ended | ||
Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2014 | |
Equity [Abstract] | |||
Beginning Balance AOCI December 31, 2015, Defined Benefit Plans Before-Tax | $ (57,660) | ||
Net actuarial gain/(loss), Defined Benefit Plans Before-Tax | (22,770) | $ (30,519) | $ (173,646) |
Translation adjustments, Defined Benefit Plans Before-Tax | 0 | ||
Other comprehensive income before reclassifications, Defined Benefit Plans Before-Tax | (22,770) | ||
Amortization of prior service cost, Defined Benefit Plans Before-Tax | 1,335 | 1,335 | 355 |
Amortization of net actuarial loss, Defined Benefit Plans Before-Tax | 27,066 | 34,381 | 23,656 |
Regulatory adjustment, Defined Benefit Plans Before-Tax | (5,584) | (5,646) | 140,308 |
Net current period other comprehensive income (loss), Defined Benefit Plans Before-Tax | 47 | (449) | (15,988) |
Less: Translation adjustment attributable to redeemable noncontrolling interest, Defined Benefit Plans Before-Tax | 0 | ||
Net current period other comprehensive income (loss) attributable to Southwest Gas Corporation, Defined Benefit Plans Before-Tax | 47 | ||
Ending Balance AOCI December 31, 2016, Defined Benefit Plans Before-Tax | (57,613) | (57,660) | |
Beginning Balance AOCI December 31, 2015, Defined Benefit Plans Tax (Expense) Benefit | 21,911 | ||
Net actuarial gain/(loss), Tax (Expense) or Benefit | 8,652 | 11,597 | 65,985 |
Translation adjustments, Defined Benefit Plans Tax (Expense) Benefit | 0 | ||
Other comprehensive income before reclassifications, Defined Benefit Plans Tax (Expense) Benefit | 8,652 | ||
Amortization of prior service cost, Defined Benefit Plans Tax (Expense) Benefit | (507) | (507) | (135) |
Amortization of net actuarial loss, Defined Benefit Plans Tax (Expense) Benefit | (10,285) | (13,065) | (8,989) |
Regulatory adjustment, Defined Benefit Plans Tax (Expense) Benefit | 2,122 | 2,146 | (53,317) |
Pension plans other comprehensive income (loss), Tax (Expense) or Benefit | (18) | 171 | 6,075 |
Less: Translation adjustment attributable to redeemable noncontrolling interest, Defined Benefit Plans Tax (Expense) Benefit | 0 | ||
Net current period other comprehensive income (loss) attributable to Southwest Gas Corporation, Defined Benefit Plans Tax (Expense) Benefit | (18) | ||
Ending Balance AOCI December 31, 2016, Defined Benefit Plans Tax (Expense) Benefit | 21,893 | 21,911 | |
Beginning Balance AOCI December 31, 2015, Defined Benefit Plans After-Tax | (35,749) | ||
Net actuarial gain/(loss), Defined Benefit Plans After-Tax | (14,118) | (18,922) | (107,661) |
Translation adjustments, Defined Benefit Plans After-Tax | 0 | ||
Other comprehensive income before reclassifications, Defined Benefit Plans After-Tax | (14,118) | ||
Amortization of prior service cost, Defined Benefit Plans After-Tax | 828 | 828 | 220 |
Amortization of net actuarial (gain)/loss, Defined Benefit Plans After-Tax | 16,781 | 21,316 | 14,667 |
Regulatory adjustment, Defined Benefit Plans After-Tax | (3,462) | ||
Net defined benefit pension plans | 29 | (278) | (9,913) |
Less: Translation adjustment attributable to redeemable noncontrolling interest, Defined Benefit Plans After-Tax | 0 | ||
Net current period other comprehensive income (loss) attributable to Southwest Gas Corporation, Defined Benefit Plans After-Tax | 29 | ||
Ending Balance AOCI December 31, 2016, Defined Benefit Plans After-Tax | (35,720) | (35,749) | |
Beginning Balance AOCI December 31, 2015, FSIRS - Before-Tax | (19,344) | ||
Translation adjustments, FSIRS - Before-Tax | 0 | ||
Other comprehensive income before reclassifications, FSIRS - Before-Tax | 0 | ||
FSIRS amounts reclassified from AOCI, FSIRS - Before-Tax | 3,345 | 3,344 | 3,345 |
Net current period other comprehensive income (loss), FSIRS - Before-Tax | 3,345 | 3,344 | 3,345 |
Less: Translation adjustment attributable to redeemable noncontrolling interest, FSIRS - Before-Tax | 0 | ||
Net current period other comprehensive income (loss) attributable to Southwest Gas Corporation, FSIRS - Before-Tax | 3,345 | ||
Ending Balance AOCI December 31, 2016, FSIRS - Before-Tax | (15,999) | (19,344) | |
Beginning Balance AOCI December 31, 2015, FSIRS - Tax (Expense) Benefit | 7,350 | ||
Translation adjustments, FSIRS - Tax (Expense) Benefit | 0 | ||
Other comprehensive income before reclassifications, FSIRS - Tax (Expense) Benefit | 0 | ||
FSIRS amounts reclassified from AOCI, FSIRS - Tax (Expense) Benefit | (1,270) | (1,271) | (1,272) |
Net current period other comprehensive income (loss), FSIRS - Tax (Expense) Benefit | (1,270) | (1,271) | (1,272) |
Less: Translation adjustment attributable to redeemable noncontrolling interest, FSIRS - Tax (Expense) Benefit | 0 | ||
Net current period other comprehensive income (loss) attributable to Southwest Gas Corporation, FSIRS - Tax (Expense) Benefit | (1,270) | ||
Ending Balance AOCI December 31, 2016, FSIRS - Tax (Expense) Benefit | 6,080 | 7,350 | |
Beginning Balance AOCI December 31, 2015, FSIRS - After-Tax | (11,994) | ||
Translation adjustments, FSIRS - After-Tax | 0 | ||
Other comprehensive income before reclassifications | 0 | ||
FSIRS amounts reclassified from AOCI, FSIRS - After-Tax | 2,075 | 2,073 | 2,073 |
Net current period other comprehensive income (loss) | 2,075 | 2,073 | 2,073 |
Less: Translation adjustment attributable to redeemable noncontrolling interest | 0 | ||
Net current period other comprehensive income (loss) attributable to Southwest Gas Corporation, FSIRS - After-Tax | 2,075 | ||
Ending Balance AOCI December 31, 2016, FSIRS - After-Tax | (9,919) | (11,994) | |
Beginning Balance AOCI December 31, 2015, Foreign Currency Items Before-Tax | (2,525) | ||
Net actuarial gain/(loss) | 0 | ||
Translation adjustments, Foreign Currency Items Before-Tax | 161 | (1,954) | (659) |
Other comprehensive income before reclassifications | 161 | (1,954) | (659) |
FSIRS amounts reclassified from AOCI, Foreign Currency Items Before-Tax | 0 | ||
Amortization of prior service cost, Foreign Currency Items Before-Tax | 0 | ||
Amortization of net actuarial loss, Foreign Currency Items Before-Tax | 0 | ||
Regulatory adjustment, Foreign Currency Items Before-Tax | 0 | ||
Net current period other comprehensive income (loss) | 161 | ||
Less: Translation adjustment attributable to redeemable noncontrolling interest, Foreign Currency Items Before-Tax | 5 | ||
Net current period other comprehensive income (loss) attributable to Southwest Gas Corporation, Foreign Currency Items Before-Tax | 156 | (1,888) | (637) |
Ending Balance AOCI December 31, 2016 | (2,369) | (2,525) | |
Beginning Balance AOCI December 31, 2015, Foreign Currency items - Tax (Expense) Benefit | 0 | ||
Net actuarial gain/(loss) | 0 | ||
Translation adjustments, Foreign Currency items - Tax (Expense) Benefit | 0 | 0 | 0 |
Other comprehensive income before reclassifications, Foreign Currency items - Tax (Expense) Benefit | 0 | ||
FSIRS amounts reclassified from AOCI, Foreign Currency items - Tax (Expense) Benefit | 0 | ||
Amortization of prior service cost ,Foreign Currency items - Tax (Expense) Benefit | 0 | ||
Amortization of net actuarial loss, Foreign Currency items - Tax (Expense) Benefit | 0 | ||
Regulatory adjustment, Foreign Currency items - Tax (Expense) Benefit | 0 | ||
Net current period other comprehensive income (loss), Foreign Currency items - Tax (Expense) Benefit | 0 | 0 | 0 |
Less: Translation adjustment attributable to redeemable noncontrolling interest, Foreign Currency items - Tax (Expense) Benefit | 0 | ||
Net current period other comprehensive income (loss) attributable to Southwest Gas Corporation, Foreign Currency items - Tax (Expense) Benefit | 0 | 0 | 0 |
Ending Balance AOCI December 31, 2016, Foreign Currency items - Tax (Expense) Benefit | 0 | 0 | |
Beginning Balance AOCI December 31, 2015, Foreign Currency items - After-Tax | (2,525) | ||
Net actuarial gain (loss) | 0 | ||
Translation adjustments, Foreign Currency items - After-Tax | 161 | (1,954) | (659) |
Other comprehensive income before reclassifications, Foreign Currency items - After-Tax | 161 | (1,954) | (659) |
FSIRS amounts reclassified from AOCI, Foreign Currency items - After-Tax | 0 | ||
Amortization of prior service cost, Foreign Currency items - After-Tax | 0 | ||
Amortization of net actuarial loss, Foreign Currency items - After-Tax | 0 | ||
Regulatory adjustment, Foreign Currency items - After-Tax | 0 | ||
Net current period other comprehensive income (loss), Foreign Currency items - After-Tax | 161 | ||
Less: Translation adjustment attributable to redeemable noncontrolling interest, Foreign Currency items - After-Tax | 5 | ||
Net current period other comprehensive income (loss) attributable to Southwest Gas Corporation, Foreign Currency Items - After-Tax | 156 | ||
Ending Balance AOCI December 31, 2016, Foreign Currency items - After-Tax | (2,369) | (2,525) | |
Beginning Balance AOCI December 31, 2015, AOCI | (50,268) | ||
Net actuarial gain (loss) | (14,118) | (18,922) | (107,661) |
Translation adjustments, AOCI | 161 | ||
Other comprehensive income before reclassifications, AOCI | (13,957) | ||
Amounts reclassified into net income (Notes 5 and 13) | 2,075 | 2,073 | 2,073 |
Amortization of prior service cost, AOCI | 828 | 828 | 220 |
Amortization of net actuarial loss | 16,781 | 21,316 | 14,667 |
Regulatory adjustment, AOCI | (3,462) | ||
Total other comprehensive income (loss), net of tax | 2,265 | (159) | $ (8,499) |
Less: Translation adjustment attributable to redeemable noncontrolling interest, AOCI | 5 | ||
Net current period other comprehensive income (loss) attributable to Southwest Gas Corporation, AOCI | 2,260 | ||
Ending Balance AOCI December 31, 2016, AOCI | $ (48,008) | $ (50,268) |
Other Comprehensive Income an70
Other Comprehensive Income and Accumulated Other Comprehensive Income ("AOCI") - Rollforward of Accumulated Other Comprehensive Income (Parenthetical) (Detail) | 12 Months Ended |
Dec. 31, 2016 | |
Equity [Abstract] | |
Other comprehensive income loss, effective income tax rate | 38.00% |
Other Comprehensive Income an71
Other Comprehensive Income and Accumulated Other Comprehensive Income ("AOCI") - Amount Recognized Before Income Tax Associated with Defined Benefit Plans in Accumulated Other Comprehensive Income (Detail) - USD ($) $ in Thousands | Dec. 31, 2016 | Dec. 31, 2015 |
Accumulated Other Comprehensive Income (Loss) [Line Items] | ||
Less: amount recognized in regulatory assets | $ 477,743 | $ 488,257 |
Recognized in AOCI | (57,613) | (57,660) |
Defined Benefit Plans [Member] | ||
Accumulated Other Comprehensive Income (Loss) [Line Items] | ||
Net actuarial (loss) gain | (430,973) | (435,269) |
Prior service cost | (5,703) | (7,038) |
Less: amount recognized in regulatory assets | 379,063 | 384,647 |
Recognized in AOCI | $ (57,613) | $ (57,660) |
Common Stock - Additional Infor
Common Stock - Additional Information (Detail) - USD ($) | Mar. 10, 2015 | Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2014 | Dec. 31, 2016 |
Value of common stock | $ 100,000,000 | ||||
Net proceeds to Company | $ 472,000 | $ 35,396,000 | $ 405,000 | ||
Common stock issued through Stock Incentive Plan, Restricted Stock/Unit Plan, and Management Incentive Plan | 105,000 | ||||
BNY Mellon Capital Markets, LLC [Member] | |||||
Common stock sold through agent | 0 | 645,225 | |||
Net proceeds to Company | $ 35,167,584 | ||||
Agent commissions | $ 355,228 |
Long-Term Debt - Schedule of Ca
Long-Term Debt - Schedule of Carrying Amounts and Estimated Fair Values of Long-Term Debt (Detail) - USD ($) $ in Thousands | Dec. 31, 2016 | Sep. 30, 2016 | Dec. 31, 2015 |
Long-term Debt, Current and Noncurrent Abstract | |||
Less: current maturities | $ (50,101) | $ (19,475) | |
Long-term debt, less current maturities | 1,549,983 | 1,551,204 | |
Variable-rate bonds [Member] | 2009 Series A, due 2039 [Member] | |||
Debt Instrument [Line Items] | |||
Unsecured debt, fair value | 50,000 | 50,000 | |
Carrying Amount [Member] | |||
Debt Instrument [Line Items] | |||
Unamortized debt issuance costs | (516) | (692) | |
Total long-term debt | 1,600,084 | 1,570,679 | |
Long-term Debt, Current and Noncurrent Abstract | |||
Less: current maturities | (50,101) | (19,475) | |
Long-term debt, less current maturities | 1,549,983 | 1,551,204 | |
Total long-term debt | 1,600,084 | 1,570,679 | |
Carrying Amount [Member] | Centuri Secured Revolving Credit Facility [Member] | |||
Debt Instrument [Line Items] | |||
Centuri term loan/secured revolving credit facility | 41,185 | 60,627 | |
Carrying Amount [Member] | IDRBs [Member] | |||
Debt Instrument [Line Items] | |||
Centuri term loan/secured revolving credit facility | 106,184 | 111,879 | |
Unsecured debt | 197,511 | 320,909 | |
Carrying Amount [Member] | Centuri Term Loan Facility [Member] | |||
Debt Instrument [Line Items] | |||
Centuri term loan/secured revolving credit facility | 106,700 | 112,571 | |
Carrying Amount [Member] | Centuri Other Debt Obligations [Member] | |||
Debt Instrument [Line Items] | |||
Centuri other debt obligations | 52,635 | 25,901 | |
Carrying Amount [Member] | Debentures [Member] | |||
Debt Instrument [Line Items] | |||
Unamortized discount and debt issuance costs | (9,931) | (6,137) | |
Notes payable | 1,197,569 | 901,363 | |
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] | Notes, 3.8%, due 2046 [Member] | |||
Debt Instrument [Line Items] | |||
Notes payable | 300,000 | $ 300,000 | 0 |
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] | Revolving Credit Facility and Commercial Paper [Member] | |||
Debt Instrument [Line Items] | |||
Line of credit facility | 5,000 | 150,000 | |
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] | |||
Debt Instrument [Line Items] | |||
Unamortized discount and debt issuance costs | (2,489) | (3,946) | |
Carrying Amount [Member] | Fixed-Rate Bonds [Member] | 4.85% 2005 Series A, due 2035 [Member] | |||
Debt Instrument [Line Items] | |||
Unsecured debt | 0 | 100,000 | |
Carrying Amount [Member] | Fixed-Rate Bonds [Member] | 4.75% 2006 Series A, due 2036 [Member] | |||
Debt Instrument [Line Items] | |||
Unsecured debt | 0 | 24,855 | |
Market Value [Member] | |||
Debt Instrument [Line Items] | |||
Centuri term loan/secured revolving credit facility | 106,819 | 112,665 | |
Centuri other debt obligations | 52,840 | 26,059 | |
Market Value [Member] | Centuri Secured Revolving Credit Facility [Member] | |||
Debt Instrument [Line Items] | |||
Centuri term loan/secured revolving credit facility | 41,292 | 60,724 | |
Market Value [Member] | Debentures [Member] | Notes, 4.45%, due 2020 [Member] | |||
Debt Instrument [Line Items] | |||
Notes payable, fair value disclosure | 129,703 | 130,273 | |
Market Value [Member] | Debentures [Member] | Notes, 6.1%, due 2041 [Member] | |||
Debt Instrument [Line Items] | |||
Notes payable, fair value disclosure | 149,734 | 141,581 | |
Market Value [Member] | Debentures [Member] | Notes, 3.875%, due 2022 [Member] | |||
Debt Instrument [Line Items] | |||
Notes payable, fair value disclosure | 254,900 | 253,600 | |
Market Value [Member] | Debentures [Member] | Notes, 4.875%, due 2043 [Member] | |||
Debt Instrument [Line Items] | |||
Notes payable, fair value disclosure | 266,793 | 251,483 | |
Market Value [Member] | Debentures [Member] | Notes, 3.8%, due 2046 [Member] | |||
Debt Instrument [Line Items] | |||
Notes payable, fair value disclosure | 283,029 | 0 | |
Market Value [Member] | Debentures [Member] | 8% Series, due 2026 [Member] | |||
Debt Instrument [Line Items] | |||
Notes payable, fair value disclosure | 94,691 | 97,035 | |
Market Value [Member] | Debentures [Member] | Medium-term notes, 7.59% series, due 2017 [Member] | |||
Debt Instrument [Line Items] | |||
Notes payable, fair value disclosure | 25,040 | 26,253 | |
Market Value [Member] | Debentures [Member] | Medium-term notes, 7.78% series, due 2022 [Member] | |||
Debt Instrument [Line Items] | |||
Notes payable, fair value disclosure | 29,290 | 29,855 | |
Market Value [Member] | Debentures [Member] | Medium-term notes, 7.92% series, due 2027 [Member] | |||
Debt Instrument [Line Items] | |||
Notes payable, fair value disclosure | 31,905 | 31,890 | |
Market Value [Member] | Debentures [Member] | Medium-term notes, 6.76% series, due 2027 [Member] | |||
Debt Instrument [Line Items] | |||
Notes payable, fair value disclosure | 8,769 | 8,684 | |
Market Value [Member] | Debentures [Member] | Revolving Credit Facility and Commercial Paper [Member] | |||
Debt Instrument [Line Items] | |||
Line of credit facility, fair value | 5,000 | 150,000 | |
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] | Fixed-Rate Bonds [Member] | 4.85% 2005 Series A, due 2035 [Member] | |||
Debt Instrument [Line Items] | |||
Unsecured debt, fair value | 0 | 100,452 | |
Market Value [Member] | Fixed-Rate Bonds [Member] | 4.75% 2006 Series A, due 2036 [Member] | |||
Debt Instrument [Line Items] | |||
Unsecured debt, fair value | $ 0 | $ 25,130 |
Long-Term Debt - Schedule of 74
Long-Term Debt - Schedule of Carrying Amounts and Estimated Fair Values of Long-Term Debt (Parenthetical) (Detail) | 1 Months Ended | 12 Months Ended | |
Sep. 30, 2016 | Dec. 31, 2016 | Dec. 31, 2015 | |
Debentures [Member] | Notes, 4.45%, due 2020 [Member] | |||
Debt Instrument [Line Items] | |||
Debt instrument interest rate | 4.45% | 4.45% | |
Debt instrument due date | Dec. 1, 2020 | Dec. 1, 2020 | |
Debentures [Member] | Notes, 6.1%, due 2041 [Member] | |||
Debt Instrument [Line Items] | |||
Debt instrument interest rate | 6.10% | 6.10% | |
Debt instrument due date | Feb. 15, 2041 | Feb. 15, 2041 | |
Debentures [Member] | Notes, 3.875%, due 2022 [Member] | |||
Debt Instrument [Line Items] | |||
Debt instrument interest rate | 3.875% | 3.875% | |
Debt instrument due date | Apr. 1, 2022 | Apr. 1, 2022 | |
Debentures [Member] | Notes, 4.875%, due 2043 [Member] | |||
Debt Instrument [Line Items] | |||
Debt instrument interest rate | 4.875% | 4.875% | |
Debt instrument due date | Oct. 1, 2043 | Oct. 1, 2043 | |
Debentures [Member] | Notes, 3.8%, due 2046 [Member] | |||
Debt Instrument [Line Items] | |||
Debt instrument interest rate | 3.80% | 3.80% | |
Debt instrument due date | Sep. 30, 2046 | Sep. 30, 2046 | |
Debentures [Member] | 8% Series, due 2026 [Member] | |||
Debt Instrument [Line Items] | |||
Debt instrument interest rate | 8.00% | 8.00% | |
Debt instrument due date | Aug. 1, 2026 | Aug. 1, 2026 | |
Debentures [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 | Jan. 17, 2017 | Jan. 17, 2017 | |
Debentures [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 | Feb. 3, 2022 | Feb. 3, 2022 | |
Debentures [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 | Jun. 24, 2027 | Jun. 24, 2027 | |
Debentures [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 | Sep. 24, 2027 | Sep. 24, 2027 | |
Variable-rate bonds [Member] | Tax-exempt Series A, due 2028 [Member] | |||
Debt Instrument [Line Items] | |||
Debt instrument due date | Dec. 1, 2028 | Dec. 1, 2028 | |
Variable-rate bonds [Member] | 2003 Series A, due 2038 [Member] | |||
Debt Instrument [Line Items] | |||
Debt instrument due date | Mar. 1, 2038 | Mar. 1, 2038 | |
Variable-rate bonds [Member] | 2008 Series A, due 2038 [Member] | |||
Debt Instrument [Line Items] | |||
Debt instrument due date | Mar. 1, 2038 | Mar. 1, 2038 | |
Fixed-Rate Bonds [Member] | 4.85% 2005 Series A, due 2035 [Member] | |||
Debt Instrument [Line Items] | |||
Debt instrument interest rate | 4.85% | ||
Debt instrument due date | Oct. 1, 2035 | ||
Fixed-Rate Bonds [Member] | 4.75% 2006 Series A, due 2036 [Member] | |||
Debt Instrument [Line Items] | |||
Debt instrument interest rate | 4.75% | ||
Debt instrument due date | Sep. 1, 2036 | ||
Market Value [Member] | Variable-rate bonds [Member] | 2009 Series A, due 2039 [Member] | |||
Debt Instrument [Line Items] | |||
Debt instrument due date | Dec. 1, 2039 | Dec. 1, 2039 |
Long-Term Debt - Additional Inf
Long-Term Debt - Additional Information (Detail) - USD ($) | 1 Months Ended | 3 Months Ended | 12 Months Ended | |||||
Jan. 31, 2017 | Sep. 30, 2016 | Jul. 31, 2016 | Feb. 29, 2016 | Sep. 30, 2016 | Mar. 31, 2016 | Dec. 31, 2016 | Dec. 31, 2015 | |
Debt Instrument [Line Items] | ||||||||
Line of credit designated for working capital purposes | $ 150,000,000 | |||||||
Minimum current borrowing usage | $ 0 | |||||||
Maximum current borrowing usage | $ 230,000,000 | |||||||
Debt instrument covenant description | Certain debt instruments contain securities ratings covenants that, if set in motion, would increase financing costs. Certain debt instruments also have leverage ratio caps and minimum net worth requirements. At December 31, 2016, the Company is in compliance with all of its covenants. | |||||||
Issuance of additional debt | $ 2,300,000,000 | |||||||
Minimum net worth | 1,100,000,000 | |||||||
Short-Term Credit Facility [Member] | ||||||||
Debt Instrument [Line Items] | ||||||||
Borrowings outstanding under facility | $ 0 | $ 18,000,000 | ||||||
Secured Revolving Credit and Term Loan Facility [Member] | ||||||||
Debt Instrument [Line Items] | ||||||||
Minimum current borrowing usage | $ 36,200,000 | |||||||
Maximum current borrowing usage | $ 83,200,000 | |||||||
Secured Revolving Credit and Term Loan Facility [Member] | Minimum [Member] | ||||||||
Debt Instrument [Line Items] | ||||||||
Commitment fee | 0.15% | |||||||
Secured Revolving Credit and Term Loan Facility [Member] | Maximum [Member] | ||||||||
Debt Instrument [Line Items] | ||||||||
Commitment fee | 0.40% | |||||||
Centuri Secured Revolving Credit Facility [Member] | ||||||||
Debt Instrument [Line Items] | ||||||||
Effective interest rate | 2.63% | |||||||
Debentures [Member] | Carrying Amount [Member] | ||||||||
Debt Instrument [Line Items] | ||||||||
Notes payable | $ 1,197,569,000 | $ 901,363,000 | ||||||
Centuri Construction Group Inc [Member] | ||||||||
Debt Instrument [Line Items] | ||||||||
Debt instrument covenant description | Certain Centuri debt instruments also have leverage ratio caps and fixed charge ratio coverage requirements. At December 31, 2016, Centuri is in compliance with all of its covenants. | |||||||
Issuance of additional debt | $ 145,000,000 | |||||||
Equity cushion relating to minimum fixed charge ratio coverage requirement | 21,000,000 | |||||||
Centuri Construction Group Inc [Member] | Secured Revolving Credit and Term Loan Facility [Member] | ||||||||
Debt Instrument [Line Items] | ||||||||
Credit facility maximum borrowing capacity | $ 300,000,000 | |||||||
Credit facility expiration date | Oct. 31, 2019 | |||||||
Debt secured by assets | $ 445,000,000 | |||||||
Centuri Construction Group Inc [Member] | Centuri Secured Revolving Credit Facility [Member] | ||||||||
Debt Instrument [Line Items] | ||||||||
Credit facility maximum borrowing capacity | $ 150,000,000 | |||||||
LIBOR [Member] | Secured Revolving Credit and Term Loan Facility [Member] | Minimum [Member] | ||||||||
Debt Instrument [Line Items] | ||||||||
Applicable margin | 1.00% | |||||||
LIBOR [Member] | Secured Revolving Credit and Term Loan Facility [Member] | Maximum [Member] | ||||||||
Debt Instrument [Line Items] | ||||||||
Applicable margin | 2.25% | |||||||
Canadian Dealer Offered Rate [Member] | Secured Revolving Credit and Term Loan Facility [Member] | Minimum [Member] | ||||||||
Debt Instrument [Line Items] | ||||||||
Applicable margin | 1.00% | |||||||
Canadian Dealer Offered Rate [Member] | Secured Revolving Credit and Term Loan Facility [Member] | Maximum [Member] | ||||||||
Debt Instrument [Line Items] | ||||||||
Applicable margin | 2.25% | |||||||
Alternate Base Rate or Canadian Base Rate [Member] | Secured Revolving Credit and Term Loan Facility [Member] | Minimum [Member] | ||||||||
Debt Instrument [Line Items] | ||||||||
Applicable margin | 0.00% | |||||||
Alternate Base Rate or Canadian Base Rate [Member] | Secured Revolving Credit and Term Loan Facility [Member] | Maximum [Member] | ||||||||
Debt Instrument [Line Items] | ||||||||
Applicable margin | 1.25% | |||||||
4.85% 2005 Series A, due 2035 [Member] | Fixed-Rate Bonds [Member] | ||||||||
Debt Instrument [Line Items] | ||||||||
Debt instrument interest rate | 4.85% | |||||||
Debt instrument due date | Oct. 1, 2035 | |||||||
4.85% 2005 Series A, due 2035 [Member] | Fixed-Rate Bonds [Member] | Carrying Amount [Member] | ||||||||
Debt Instrument [Line Items] | ||||||||
Unsecured debt | $ 0 | $ 100,000,000 | ||||||
4.85% 2005 Series A, due 2035 [Member] | Early Redemption of Debt [Member] | Fixed-Rate Bonds [Member] | ||||||||
Debt Instrument [Line Items] | ||||||||
Unsecured debt | $ 100,000,000 | |||||||
Debt instrument, original debt due date of debt year | 2,035 | |||||||
Debt instrument interest rate | 4.85% | |||||||
4.75% 2006 Series A, due 2036 [Member] | Fixed-Rate Bonds [Member] | ||||||||
Debt Instrument [Line Items] | ||||||||
Debt instrument interest rate | 4.75% | |||||||
Debt instrument due date | Sep. 1, 2036 | |||||||
4.75% 2006 Series A, due 2036 [Member] | Fixed-Rate Bonds [Member] | Carrying Amount [Member] | ||||||||
Debt Instrument [Line Items] | ||||||||
Unsecured debt | $ 0 | $ 24,855,000 | ||||||
4.75% 2006 Series A, due 2036 [Member] | Early Redemption of Debt [Member] | Fixed-Rate Bonds [Member] | ||||||||
Debt Instrument [Line Items] | ||||||||
Unsecured debt | $ 24,900,000 | $ 24,900,000 | ||||||
Debt instrument, original debt due date of debt year | 2,036 | |||||||
Debt instrument interest rate | 4.75% | 4.75% | ||||||
Southwest Gas Credit Facility [Member] | ||||||||
Debt Instrument [Line Items] | ||||||||
Credit facility maximum borrowing capacity | $ 300,000,000 | |||||||
Line of credit designated as long term debt | 150,000,000 | |||||||
Line of credit designated for working capital purposes | $ 150,000,000 | |||||||
Credit facility expiration date | Mar. 1, 2021 | |||||||
Effective interest rate | 5.21% | |||||||
Southwest Gas Credit Facility [Member] | Long-term Debt [Member] | ||||||||
Debt Instrument [Line Items] | ||||||||
Borrowings outstanding under facility | $ 5,000,000 | |||||||
Southwest Gas Credit Facility [Member] | Before Amendment [Member] | ||||||||
Debt Instrument [Line Items] | ||||||||
Previous credit facility expiration date | Mar. 1, 2020 | |||||||
Southwest Gas Credit Facility [Member] | LIBOR [Member] | ||||||||
Debt Instrument [Line Items] | ||||||||
Applicable margin | 1.00% | |||||||
Southwest Gas Credit Facility [Member] | Alternative Base Rate [Member] | ||||||||
Debt Instrument [Line Items] | ||||||||
Applicable margin | 0.00% | |||||||
Commercial Paper Program [Member] | ||||||||
Debt Instrument [Line Items] | ||||||||
Credit facility maximum borrowing capacity | $ 50,000,000 | |||||||
Borrowings outstanding under facility | $ 0 | |||||||
Notes, 3.8%, due 2046 [Member] | Debentures [Member] | ||||||||
Debt Instrument [Line Items] | ||||||||
Debt instrument interest rate | 3.80% | 3.80% | 3.80% | |||||
Debt instrument due date | Sep. 30, 2046 | Sep. 30, 2046 | ||||||
Debt instrument discount percent at issuance | 0.302% | 0.302% | ||||||
Notes, 3.8%, due 2046 [Member] | Debentures [Member] | Carrying Amount [Member] | ||||||||
Debt Instrument [Line Items] | ||||||||
Notes payable | $ 300,000,000 | $ 300,000,000 | $ 300,000,000 | $ 0 | ||||
Centuri Term Loan Facility [Member] | Centuri Construction Group Inc [Member] | ||||||||
Debt Instrument [Line Items] | ||||||||
Credit facility, face amount | $ 150,000,000 | |||||||
Medium-term notes, 7.59% series, due 2017 [Member] | Debentures [Member] | ||||||||
Debt Instrument [Line Items] | ||||||||
Debt instrument interest rate | 7.59% | 7.59% | ||||||
Debt instrument due date | Jan. 17, 2017 | Jan. 17, 2017 | ||||||
Medium-term notes, 7.59% series, due 2017 [Member] | Debentures [Member] | Carrying Amount [Member] | ||||||||
Debt Instrument [Line Items] | ||||||||
Notes payable | $ 25,000,000 | $ 25,000,000 | ||||||
Medium-term notes, 7.59% series, due 2017 [Member] | Subsequent Event [Member] | ||||||||
Debt Instrument [Line Items] | ||||||||
Debt instrument interest rate | 7.59% | |||||||
Repayments of medium term notes | $ 25,000,000 |
Long-Term Debt - Summary of Eff
Long-Term Debt - Summary of Effective Interest Rates on Variable-Rate IDRBs (Detail) | Dec. 31, 2016 | Dec. 31, 2015 |
2003 Series A, due 2038 [Member] | ||
Debt Instrument [Line Items] | ||
Effective interest rates | 1.47% | 0.87% |
2008 Series A, due 2038 [Member] | ||
Debt Instrument [Line Items] | ||
Effective interest rates | 1.53% | 0.87% |
2009 Series A, due 2039 [Member] | ||
Debt Instrument [Line Items] | ||
Effective interest rates | 1.43% | 0.75% |
Tax-exempt Series A, due 2028 [Member] | ||
Debt Instrument [Line Items] | ||
Effective interest rates | 1.51% | 0.81% |
Long-Term Debt - Estimated Matu
Long-Term Debt - Estimated Maturities of Long-Term Debt (Detail) $ in Thousands | Dec. 31, 2016USD ($) |
Debt Disclosure [Abstract] | |
2,017 | $ 50,101 |
2,018 | 24,082 |
2,019 | 134,534 |
2,020 | 134,452 |
2,021 | $ 7,815 |
Short-Term Debt - Additional In
Short-Term Debt - Additional Information (Detail) - USD ($) | 12 Months Ended | |
Dec. 31, 2016 | Dec. 31, 2015 | |
Short-term Debt [Line Items] | ||
Line of credit designated for working capital purposes | $ 150,000,000 | |
Short-term borrowings outstanding on the credit facility | 0 | $ 18,000,000 |
March 2021 [Member] | ||
Short-term Debt [Line Items] | ||
Credit facility maximum borrowing capacity | $ 300,000,000 | |
Credit facility expiration date | Mar. 31, 2021 |
Commitments and Contingencies -
Commitments and Contingencies - Additional Information (Detail) $ in Millions | Dec. 31, 2016USD ($) |
Commitments and Contingencies Disclosure [Abstract] | |
Self-insured retention amount associated with general liability claims | $ 1 |
Additional self-insured retention amount of general liability | $ 4 |
Pension and Other Postretirem80
Pension and Other Postretirement Benefits - Additional Information (Detail) $ in Millions | 3 Months Ended | 12 Months Ended | |
Dec. 31, 2016USD ($) | Sep. 30, 2016Participants | Dec. 31, 2016USD ($) | |
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items] | |||
Maximum contribution of employer | 3.50% | ||
Deferment of annual cash compensation | 100.00% | ||
Matching contribution of employer | 3.50% | ||
Deferred compensation payments on retirement | Upon retirement, payments of compensation deferred, plus interest, are made in equal monthly installments over 10, 15, or 20 years, as elected by the participant. | ||
Additional Deferred Compensation Payment Options, period of payment, years | 5 years | ||
Deferred compensation, percentage of multiple interest rate | 150.00% | ||
Description of specific offer to select employees | About one-half of the approximate 800 participants subject to the offer accepted the offer, resulting in an approximate $30 million payment from pension assets paid in the fourth quarter of 2016. | ||
Number of employees offered a lump-sum payout | Participants | 800 | ||
Lump sum pension payment to be paid | $ 30 | ||
Increments of changes to the discount rate, basis points | 0.25% | ||
Future estimated funding amount | $ 39 | ||
Maximum [Member] | |||
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items] | |||
Per capita cost of covered health care benefits medical rate trend assumption | 7.00% | ||
Minimum [Member] | |||
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items] | |||
Per capita cost of covered health care benefits medical rate trend assumption | 4.50% | ||
Qualified Retirement Plan [Member] | |||
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items] | |||
Future estimated funding amount | $ 36 |
Pension and Other Postretirem81
Pension and Other Postretirement Benefits - Cost of Retirement Plan (Detail) - USD ($) $ in Thousands | 12 Months Ended | ||
Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2014 | |
Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Abstract] | |||
Employee Investment Plan cost | $ 4,976 | $ 5,072 | $ 4,816 |
Pension and Other Postretirem82
Pension and Other Postretirement Benefits - Schedule of Percentage Range of Target Portfolio (Detail) | 12 Months Ended |
Dec. 31, 2016 | |
Minimum [Member] | Equity Securities [Member] | |
Percentage of Investment in Retirement Plan [Line Items] | |
Percentage range of investment | 63.00% |
Minimum [Member] | Debt Securities [Member] | |
Percentage of Investment in Retirement Plan [Line Items] | |
Percentage range of investment | 33.00% |
Maximum [Member] | Equity Securities [Member] | |
Percentage of Investment in Retirement Plan [Line Items] | |
Percentage range of investment | 67.00% |
Maximum [Member] | Debt Securities [Member] | |
Percentage of Investment in Retirement Plan [Line Items] | |
Percentage range of investment | 37.00% |
Maximum [Member] | Other Up To [Member] | |
Percentage of Investment in Retirement Plan [Line Items] | |
Percentage range of investment | 1.00% |
Pension and Other Postretirem83
Pension and Other Postretirement Benefits - Schedule of Assumptions Used (Detail) | 12 Months Ended | |
Dec. 31, 2016 | Dec. 31, 2015 | |
Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Abstract] | ||
Discount rate | 4.50% | 4.50% |
Weighted-average rate of compensation increase | 3.25% | 3.25% |
Asset return assumption | 7.00% | 7.25% |
Pension and Other Postretirem84
Pension and Other Postretirement Benefits - Schedule of Amounts Recognized in Balance Sheet and Income Statement (Detail) - USD ($) $ in Thousands | 12 Months Ended | ||
Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2014 | |
Qualified Retirement Plan [Member] | |||
Change in benefit obligations | |||
Change in benefit obligations Benefit obligation for service rendered to date at beginning of year (PBO/PBO/APBO) | $ 1,044,817 | $ 1,060,240 | |
Service cost | 22,833 | 25,123 | $ 21,360 |
Interest cost | 46,027 | 44,229 | 43,440 |
Actuarial loss (gain) | 8,550 | (44,553) | |
Benefits paid | (73,874) | (40,222) | |
Benefit obligation at end of year (PBO/PBO/APBO) | 1,048,353 | 1,044,817 | 1,060,240 |
Change in plan assets | |||
Market value of plan assets, beginning balance | 736,880 | 754,796 | |
Actual return on plan assets | 39,956 | (13,694) | |
Employer contributions | 36,000 | 36,000 | |
Benefits paid | (73,874) | (40,222) | |
Market value of plan assets, ending balance | 738,962 | 736,880 | 754,796 |
Funded status at year end | $ (309,391) | $ (307,937) | |
Weighted-average assumptions (benefit obligation) | |||
Discount rate | 4.50% | 4.50% | |
Weighted-average rate of compensation increase | 3.25% | 3.25% | |
SERP [Member] | |||
Change in benefit obligations | |||
Change in benefit obligations Benefit obligation for service rendered to date at beginning of year (PBO/PBO/APBO) | $ 42,720 | $ 41,176 | |
Service cost | 331 | 320 | 292 |
Interest cost | 1,859 | 1,695 | 1,745 |
Actuarial loss (gain) | 1,347 | 2,322 | |
Benefits paid | (2,946) | (2,793) | |
Benefit obligation at end of year (PBO/PBO/APBO) | 43,311 | 42,720 | 41,176 |
Change in plan assets | |||
Market value of plan assets, beginning balance | 0 | 0 | |
Actual return on plan assets | 0 | 0 | |
Employer contributions | 2,946 | 2,793 | |
Benefits paid | (2,946) | (2,793) | |
Market value of plan assets, ending balance | 0 | 0 | 0 |
Funded status at year end | $ (43,311) | $ (42,720) | |
Weighted-average assumptions (benefit obligation) | |||
Discount rate | 4.50% | 4.50% | |
Weighted-average rate of compensation increase | 3.25% | 3.25% | |
PBOP [Member] | |||
Change in benefit obligations | |||
Change in benefit obligations Benefit obligation for service rendered to date at beginning of year (PBO/PBO/APBO) | $ 72,632 | $ 72,202 | |
Service cost | 1,499 | 1,641 | 1,101 |
Interest cost | 3,180 | 2,999 | 2,829 |
Actuarial loss (gain) | (2,060) | (3,251) | |
Benefits paid | (1,386) | (959) | |
Benefit obligation at end of year (PBO/PBO/APBO) | 73,865 | 72,632 | 72,202 |
Change in plan assets | |||
Market value of plan assets, beginning balance | 43,584 | 44,892 | |
Actual return on plan assets | 4,818 | (1,034) | |
Employer contributions | 0 | 0 | |
Benefits paid | (289) | (274) | |
Market value of plan assets, ending balance | 48,113 | 43,584 | $ 44,892 |
Funded status at year end | $ (25,752) | $ (29,048) | |
Weighted-average assumptions (benefit obligation) | |||
Discount rate | 4.50% | 4.50% |
Pension and Other Postretirem85
Pension and Other Postretirement Benefits - Schedule of Accumulated Benefit Obligation (Detail) - USD ($) $ in Thousands | Dec. 31, 2016 | Dec. 31, 2015 |
Qualified Retirement Plan [Member] | ||
Defined Benefit Plan Disclosure [Line Items] | ||
Accumulated benefit obligation | $ 939,002 | $ 922,992 |
SERP [Member] | ||
Defined Benefit Plan Disclosure [Line Items] | ||
Accumulated benefit obligation | $ 40,852 | $ 39,270 |
Pension and Other Postretirem86
Pension and Other Postretirement Benefits - Schedule of Expected Benefit Payments (Detail) $ in Millions | Dec. 31, 2016USD ($) |
Pension [Member] | |
Defined Benefit Plan Disclosure [Line Items] | |
2,017 | $ 48.6 |
2,018 | 50.1 |
2,019 | 51.5 |
2,020 | 53.2 |
2,021 | 55.1 |
2022-2026 | 294.2 |
PBOP [Member] | |
Defined Benefit Plan Disclosure [Line Items] | |
2,017 | 4.1 |
2,018 | 4.3 |
2,019 | 4.4 |
2,020 | 4.5 |
2,021 | 4.5 |
2022-2026 | 20.6 |
SERP [Member] | |
Defined Benefit Plan Disclosure [Line Items] | |
2,017 | 2.9 |
2,018 | 2.9 |
2,019 | 2.9 |
2,020 | 2.9 |
2,021 | 2.9 |
2022-2026 | $ 14.4 |
Pension and Other Postretirem87
Pension and Other Postretirement Benefits - Schedule of Net Periodic Benefit Cost and Weighted-Average Assumptions (Detail) - USD ($) $ in Thousands | 12 Months Ended | ||
Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2014 | |
Defined Benefit Plan Disclosure [Line Items] | |||
Net periodic benefit cost | $ 44,423 | $ 50,451 | $ 38,172 |
Weighted-average assumptions (net benefit cost) | |||
Discount rate | 4.50% | 4.50% | |
Expected return on plan assets | 7.00% | 7.25% | |
Weighted-average rate of compensation increase | 3.25% | 3.25% | |
Qualified Retirement Plan [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Service cost | $ 22,833 | $ 25,123 | 21,360 |
Interest cost | 46,027 | 44,229 | 43,440 |
Expected return on plan assets | (56,558) | (57,808) | (53,342) |
Amortization of prior service cost | 0 | 0 | 0 |
Amortization of net actuarial loss | 25,266 | 32,743 | 22,873 |
Net periodic benefit cost | $ 37,568 | $ 44,287 | $ 34,331 |
Weighted-average assumptions (net benefit cost) | |||
Discount rate | 4.50% | 4.25% | 5.00% |
Expected return on plan assets | 7.25% | 7.75% | 7.75% |
Weighted-average rate of compensation increase | 3.25% | 2.75% | 3.25% |
SERP [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Service cost | $ 331 | $ 320 | $ 292 |
Interest cost | 1,859 | 1,695 | 1,745 |
Expected return on plan assets | 0 | 0 | 0 |
Amortization of prior service cost | 0 | 0 | 0 |
Amortization of net actuarial loss | 1,383 | 1,293 | 783 |
Net periodic benefit cost | $ 3,573 | $ 3,308 | $ 2,820 |
Weighted-average assumptions (net benefit cost) | |||
Discount rate | 4.50% | 4.25% | 5.00% |
Weighted-average rate of compensation increase | 3.25% | 2.75% | 3.25% |
PBOP [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Service cost | $ 1,499 | $ 1,641 | $ 1,101 |
Interest cost | 3,180 | 2,999 | 2,829 |
Expected return on plan assets | (3,149) | (3,464) | (3,264) |
Amortization of prior service cost | 1,335 | 1,335 | 355 |
Amortization of net actuarial loss | 417 | 345 | 0 |
Net periodic benefit cost | $ 3,282 | $ 2,856 | $ 1,021 |
Weighted-average assumptions (net benefit cost) | |||
Discount rate | 4.50% | 4.25% | 5.00% |
Expected return on plan assets | 7.25% | 7.75% | 7.75% |
Pension and Other Postretirem88
Pension and Other Postretirement Benefits - Schedule of Other Changes in Plan Assets and Benefit Obligations Recognized in Net Periodic Benefit Cost and Other Comprehensive Income (Detail) - USD ($) $ in Thousands | 12 Months Ended | ||
Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2014 | |
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items] | |||
Net actuarial loss (gain) | $ 22,770 | $ 30,519 | $ 173,646 |
Amortization of prior service cost | (1,335) | (1,335) | (355) |
Amortization of net actuarial loss | (27,066) | (34,381) | (23,656) |
Prior service cost | 0 | 0 | 6,661 |
Regulatory adjustment | 5,584 | 5,646 | (140,308) |
Recognized in other comprehensive (income) loss | (47) | 449 | 15,988 |
Net periodic benefit costs recognized in net income | 44,423 | 50,451 | 38,172 |
Total of amount recognized in net periodic benefit cost and other comprehensive (income) loss | 44,376 | 50,900 | 54,160 |
Qualified Retirement Plan [Member] | |||
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items] | |||
Net actuarial loss (gain) | 25,153 | 26,949 | 163,215 |
Amortization of prior service cost | 0 | 0 | 0 |
Amortization of net actuarial loss | (25,266) | (32,743) | (22,872) |
Prior service cost | 0 | 0 | 0 |
Regulatory adjustment | 102 | 5,214 | (129,031) |
Recognized in other comprehensive (income) loss | (11) | (580) | 11,312 |
Net periodic benefit costs recognized in net income | 37,568 | 44,287 | 34,331 |
Total of amount recognized in net periodic benefit cost and other comprehensive (income) loss | 37,557 | 43,707 | 45,643 |
SERP [Member] | |||
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items] | |||
Net actuarial loss (gain) | 1,347 | 2,322 | 5,460 |
Amortization of prior service cost | 0 | 0 | 0 |
Amortization of net actuarial loss | (1,383) | (1,293) | (784) |
Prior service cost | 0 | 0 | 0 |
Regulatory adjustment | 0 | 0 | 0 |
Recognized in other comprehensive (income) loss | (36) | 1,029 | 4,676 |
Net periodic benefit costs recognized in net income | 3,573 | 3,308 | 2,820 |
Total of amount recognized in net periodic benefit cost and other comprehensive (income) loss | 3,537 | 4,337 | 7,496 |
PBOP [Member] | |||
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items] | |||
Net actuarial loss (gain) | (3,730) | 1,248 | 4,971 |
Amortization of prior service cost | (1,335) | (1,335) | (355) |
Amortization of net actuarial loss | (417) | (345) | 0 |
Prior service cost | 0 | 0 | 6,661 |
Regulatory adjustment | 5,482 | 432 | (11,277) |
Recognized in other comprehensive (income) loss | 0 | 0 | 0 |
Net periodic benefit costs recognized in net income | 3,282 | 2,856 | 1,021 |
Total of amount recognized in net periodic benefit cost and other comprehensive (income) loss | $ 3,282 | $ 2,856 | $ 1,021 |
Pension and Other Postretirem89
Pension and Other Postretirement Benefits - Schedule of Fair Value of Plan Assets (Detail) - USD ($) $ in Thousands | 12 Months Ended | ||
Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2014 | |
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets, including insurance contracts | $ 787,074 | $ 783,323 | |
Assets at Fair Value [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 783,626 | 521,638 | |
Commingled Equity Funds [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 0 | 257,966 | |
Insurance Company General Account Contracts (Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Contract value of insurance contracts | 3,448 | 3,719 | |
Level 1 - Quoted Prices in Active Markets for Identical Financial Assets [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 24,922 | 364,610 | |
Level 1 - Quoted Prices in Active Markets for Identical Financial Assets [Member] | Agriculture [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 0 | 7,230 | |
Level 1 - Quoted Prices in Active Markets for Identical Financial Assets [Member] | Capital Equipment [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 0 | 549 | |
Level 1 - Quoted Prices in Active Markets for Identical Financial Assets [Member] | Chemicals/Materials [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 0 | 3,402 | |
Level 1 - Quoted Prices in Active Markets for Identical Financial Assets [Member] | Consumer Goods [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 0 | 42,256 | |
Level 1 - Quoted Prices in Active Markets for Identical Financial Assets [Member] | Energy and Mining [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 0 | 11,395 | |
Level 1 - Quoted Prices in Active Markets for Identical Financial Assets [Member] | Finance/Insurance [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 0 | 30,849 | |
Level 1 - Quoted Prices in Active Markets for Identical Financial Assets [Member] | Healthcare [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 0 | 39,059 | |
Level 1 - Quoted Prices in Active Markets for Identical Financial Assets [Member] | Information Technology [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 0 | 30,099 | |
Level 1 - Quoted Prices in Active Markets for Identical Financial Assets [Member] | Services [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 0 | 12,708 | |
Level 1 - Quoted Prices in Active Markets for Identical Financial Assets [Member] | Telecommunications/Internet/Media [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 0 | 26,653 | |
Level 1 - Quoted Prices in Active Markets for Identical Financial Assets [Member] | Other [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 0 | 9,312 | |
Level 1 - Quoted Prices in Active Markets for Identical Financial Assets [Member] | Real Estate Investment Trusts [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 0 | 5,159 | |
Level 1 - Quoted Prices in Active Markets for Identical Financial Assets [Member] | Mutual Funds [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 24,922 | 111,468 | |
Level 1 - Quoted Prices in Active Markets for Identical Financial Assets [Member] | Government Fixed Income Securities [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 0 | 34,478 | |
Level 1 - Quoted Prices in Active Markets for Identical Financial Assets [Member] | Futures Contracts [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 0 | (7) | |
Level 2 - Significant Other Observable Inputs [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 758,704 | 157,028 | |
Level 2 - Significant Other Observable Inputs [Member] | Other [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 0 | 31,917 | |
Level 2 - Significant Other Observable Inputs [Member] | Real Estate Investment Trusts [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 0 | 2,007 | |
Level 2 - Significant Other Observable Inputs [Member] | International [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 299,808 | 0 | |
Level 2 - Significant Other Observable Inputs [Member] | Large and Medium Capitalization [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 125,253 | 0 | |
Level 2 - Significant Other Observable Inputs [Member] | Small Capitalization [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 26,763 | 0 | |
Level 2 - Significant Other Observable Inputs [Member] | Emerging Markets [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 46,733 | 0 | |
Level 2 - Significant Other Observable Inputs [Member] | U S Corporate Bonds [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 166,152 | 0 | |
Level 2 - Significant Other Observable Inputs [Member] | US Debt Market Long Duration [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 79,781 | 0 | |
Level 2 - Significant Other Observable Inputs [Member] | US Treasury Securities [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 8,937 | 0 | |
Level 2 - Significant Other Observable Inputs [Member] | Pooled Funds and Mutual Funds [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 5,105 | 15,604 | |
Level 2 - Significant Other Observable Inputs [Member] | Government Fixed Income and Mortgage Backed Securities [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 172 | 51,046 | |
Level 2 - Significant Other Observable Inputs [Member] | Asset-Backed and Mortgage-Backed [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 0 | 24,243 | |
Level 2 - Significant Other Observable Inputs [Member] | Banking [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 0 | 21,478 | |
Level 2 - Significant Other Observable Inputs [Member] | Insurance [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 0 | 5,042 | |
Level 2 - Significant Other Observable Inputs [Member] | Utilities [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 0 | 3,940 | |
Level 2 - Significant Other Observable Inputs [Member] | State and Local Obligations [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 0 | 978 | |
Level 2 - Significant Other Observable Inputs [Member] | Preferred Securities [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 0 | 571 | |
Level 2 - Significant Other Observable Inputs [Member] | Convertible Securities [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 0 | 202 | |
Qualified Retirement Plan [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 738,962 | 736,880 | $ 754,796 |
Fair value of plan assets, including insurance contracts | 738,962 | 739,684 | |
Qualified Retirement Plan [Member] | Assets at Fair Value [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 735,514 | 485,454 | |
Qualified Retirement Plan [Member] | Commingled Equity Funds [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 0 | 250,511 | |
Qualified Retirement Plan [Member] | Insurance Company General Account Contracts (Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Contract value of insurance contracts | 3,448 | 3,719 | |
Qualified Retirement Plan [Member] | Level 1 - Quoted Prices in Active Markets for Identical Financial Assets [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 0 | 333,310 | |
Qualified Retirement Plan [Member] | Level 1 - Quoted Prices in Active Markets for Identical Financial Assets [Member] | Agriculture [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 0 | 7,021 | |
Qualified Retirement Plan [Member] | Level 1 - Quoted Prices in Active Markets for Identical Financial Assets [Member] | Capital Equipment [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 0 | 533 | |
Qualified Retirement Plan [Member] | Level 1 - Quoted Prices in Active Markets for Identical Financial Assets [Member] | Chemicals/Materials [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 0 | 3,304 | |
Qualified Retirement Plan [Member] | Level 1 - Quoted Prices in Active Markets for Identical Financial Assets [Member] | Consumer Goods [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 0 | 41,035 | |
Qualified Retirement Plan [Member] | Level 1 - Quoted Prices in Active Markets for Identical Financial Assets [Member] | Energy and Mining [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 0 | 11,066 | |
Qualified Retirement Plan [Member] | Level 1 - Quoted Prices in Active Markets for Identical Financial Assets [Member] | Finance/Insurance [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 0 | 29,957 | |
Qualified Retirement Plan [Member] | Level 1 - Quoted Prices in Active Markets for Identical Financial Assets [Member] | Healthcare [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 0 | 37,930 | |
Qualified Retirement Plan [Member] | Level 1 - Quoted Prices in Active Markets for Identical Financial Assets [Member] | Information Technology [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 0 | 29,229 | |
Qualified Retirement Plan [Member] | Level 1 - Quoted Prices in Active Markets for Identical Financial Assets [Member] | Services [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 0 | 12,341 | |
Qualified Retirement Plan [Member] | Level 1 - Quoted Prices in Active Markets for Identical Financial Assets [Member] | Telecommunications/Internet/Media [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 0 | 25,883 | |
Qualified Retirement Plan [Member] | Level 1 - Quoted Prices in Active Markets for Identical Financial Assets [Member] | Other [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 0 | 9,043 | |
Qualified Retirement Plan [Member] | Level 1 - Quoted Prices in Active Markets for Identical Financial Assets [Member] | Real Estate Investment Trusts [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 0 | 5,010 | |
Qualified Retirement Plan [Member] | Level 1 - Quoted Prices in Active Markets for Identical Financial Assets [Member] | Mutual Funds [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 0 | 87,483 | |
Qualified Retirement Plan [Member] | Level 1 - Quoted Prices in Active Markets for Identical Financial Assets [Member] | Government Fixed Income Securities [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 0 | 33,482 | |
Qualified Retirement Plan [Member] | Level 1 - Quoted Prices in Active Markets for Identical Financial Assets [Member] | Futures Contracts [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 0 | (7) | |
Qualified Retirement Plan [Member] | Level 2 - Significant Other Observable Inputs [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 735,514 | 152,144 | |
Qualified Retirement Plan [Member] | Level 2 - Significant Other Observable Inputs [Member] | Other [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 0 | 30,995 | |
Qualified Retirement Plan [Member] | Level 2 - Significant Other Observable Inputs [Member] | Real Estate Investment Trusts [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 0 | 1,949 | |
Qualified Retirement Plan [Member] | Level 2 - Significant Other Observable Inputs [Member] | International [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 290,668 | 0 | |
Qualified Retirement Plan [Member] | Level 2 - Significant Other Observable Inputs [Member] | Large and Medium Capitalization [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 121,434 | 0 | |
Qualified Retirement Plan [Member] | Level 2 - Significant Other Observable Inputs [Member] | Small Capitalization [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 25,947 | 0 | |
Qualified Retirement Plan [Member] | Level 2 - Significant Other Observable Inputs [Member] | Emerging Markets [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 45,309 | 0 | |
Qualified Retirement Plan [Member] | Level 2 - Significant Other Observable Inputs [Member] | U S Corporate Bonds [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 161,086 | 0 | |
Qualified Retirement Plan [Member] | Level 2 - Significant Other Observable Inputs [Member] | US Debt Market Long Duration [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 77,349 | 0 | |
Qualified Retirement Plan [Member] | Level 2 - Significant Other Observable Inputs [Member] | US Treasury Securities [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 8,665 | 0 | |
Qualified Retirement Plan [Member] | Level 2 - Significant Other Observable Inputs [Member] | Pooled Funds and Mutual Funds [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 4,889 | 14,808 | |
Qualified Retirement Plan [Member] | Level 2 - Significant Other Observable Inputs [Member] | Government Fixed Income and Mortgage Backed Securities [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 167 | 49,571 | |
Qualified Retirement Plan [Member] | Level 2 - Significant Other Observable Inputs [Member] | Asset-Backed and Mortgage-Backed [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 0 | 23,542 | |
Qualified Retirement Plan [Member] | Level 2 - Significant Other Observable Inputs [Member] | Banking [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 0 | 20,857 | |
Qualified Retirement Plan [Member] | Level 2 - Significant Other Observable Inputs [Member] | Insurance [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 0 | 4,896 | |
Qualified Retirement Plan [Member] | Level 2 - Significant Other Observable Inputs [Member] | Utilities [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 0 | 3,826 | |
Qualified Retirement Plan [Member] | Level 2 - Significant Other Observable Inputs [Member] | State and Local Obligations [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 0 | 950 | |
Qualified Retirement Plan [Member] | Level 2 - Significant Other Observable Inputs [Member] | Preferred Securities [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 0 | 554 | |
Qualified Retirement Plan [Member] | Level 2 - Significant Other Observable Inputs [Member] | Convertible Securities [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 0 | 196 | |
PBOP [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 48,113 | 43,584 | $ 44,892 |
Fair value of plan assets, including insurance contracts | 48,112 | 43,639 | |
PBOP [Member] | Assets at Fair Value [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 48,112 | 36,184 | |
PBOP [Member] | Commingled Equity Funds [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 0 | 7,455 | |
PBOP [Member] | Insurance Company General Account Contracts (Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Contract value of insurance contracts | 0 | 0 | |
PBOP [Member] | Level 1 - Quoted Prices in Active Markets for Identical Financial Assets [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 24,922 | 31,300 | |
PBOP [Member] | Level 1 - Quoted Prices in Active Markets for Identical Financial Assets [Member] | Agriculture [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 0 | 209 | |
PBOP [Member] | Level 1 - Quoted Prices in Active Markets for Identical Financial Assets [Member] | Capital Equipment [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 0 | 16 | |
PBOP [Member] | Level 1 - Quoted Prices in Active Markets for Identical Financial Assets [Member] | Chemicals/Materials [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 0 | 98 | |
PBOP [Member] | Level 1 - Quoted Prices in Active Markets for Identical Financial Assets [Member] | Consumer Goods [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 0 | 1,221 | |
PBOP [Member] | Level 1 - Quoted Prices in Active Markets for Identical Financial Assets [Member] | Energy and Mining [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 0 | 329 | |
PBOP [Member] | Level 1 - Quoted Prices in Active Markets for Identical Financial Assets [Member] | Finance/Insurance [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 0 | 892 | |
PBOP [Member] | Level 1 - Quoted Prices in Active Markets for Identical Financial Assets [Member] | Healthcare [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 0 | 1,129 | |
PBOP [Member] | Level 1 - Quoted Prices in Active Markets for Identical Financial Assets [Member] | Information Technology [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 0 | 870 | |
PBOP [Member] | Level 1 - Quoted Prices in Active Markets for Identical Financial Assets [Member] | Services [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 0 | 367 | |
PBOP [Member] | Level 1 - Quoted Prices in Active Markets for Identical Financial Assets [Member] | Telecommunications/Internet/Media [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 0 | 770 | |
PBOP [Member] | Level 1 - Quoted Prices in Active Markets for Identical Financial Assets [Member] | Other [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 0 | 269 | |
PBOP [Member] | Level 1 - Quoted Prices in Active Markets for Identical Financial Assets [Member] | Real Estate Investment Trusts [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 0 | 149 | |
PBOP [Member] | Level 1 - Quoted Prices in Active Markets for Identical Financial Assets [Member] | Mutual Funds [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 24,922 | 23,985 | |
PBOP [Member] | Level 1 - Quoted Prices in Active Markets for Identical Financial Assets [Member] | Government Fixed Income Securities [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 0 | 996 | |
PBOP [Member] | Level 1 - Quoted Prices in Active Markets for Identical Financial Assets [Member] | Futures Contracts [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 0 | 0 | |
PBOP [Member] | Level 2 - Significant Other Observable Inputs [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 23,190 | 4,884 | |
PBOP [Member] | Level 2 - Significant Other Observable Inputs [Member] | Other [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 0 | 922 | |
PBOP [Member] | Level 2 - Significant Other Observable Inputs [Member] | Real Estate Investment Trusts [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 0 | 58 | |
PBOP [Member] | Level 2 - Significant Other Observable Inputs [Member] | International [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 9,140 | 0 | |
PBOP [Member] | Level 2 - Significant Other Observable Inputs [Member] | Large and Medium Capitalization [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 3,819 | 0 | |
PBOP [Member] | Level 2 - Significant Other Observable Inputs [Member] | Small Capitalization [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 816 | 0 | |
PBOP [Member] | Level 2 - Significant Other Observable Inputs [Member] | Emerging Markets [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 1,424 | 0 | |
PBOP [Member] | Level 2 - Significant Other Observable Inputs [Member] | U S Corporate Bonds [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 5,066 | 0 | |
PBOP [Member] | Level 2 - Significant Other Observable Inputs [Member] | US Debt Market Long Duration [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 2,432 | 0 | |
PBOP [Member] | Level 2 - Significant Other Observable Inputs [Member] | US Treasury Securities [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 272 | 0 | |
PBOP [Member] | Level 2 - Significant Other Observable Inputs [Member] | Pooled Funds and Mutual Funds [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 216 | 796 | |
PBOP [Member] | Level 2 - Significant Other Observable Inputs [Member] | Government Fixed Income and Mortgage Backed Securities [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 5 | 1,475 | |
PBOP [Member] | Level 2 - Significant Other Observable Inputs [Member] | Asset-Backed and Mortgage-Backed [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 0 | 701 | |
PBOP [Member] | Level 2 - Significant Other Observable Inputs [Member] | Banking [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 0 | 621 | |
PBOP [Member] | Level 2 - Significant Other Observable Inputs [Member] | Insurance [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 0 | 146 | |
PBOP [Member] | Level 2 - Significant Other Observable Inputs [Member] | Utilities [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 0 | 114 | |
PBOP [Member] | Level 2 - Significant Other Observable Inputs [Member] | State and Local Obligations [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 0 | 28 | |
PBOP [Member] | Level 2 - Significant Other Observable Inputs [Member] | Preferred Securities [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | 0 | 17 | |
PBOP [Member] | Level 2 - Significant Other Observable Inputs [Member] | Convertible Securities [Member] | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Fair value of plan assets | $ 0 | $ 6 |
Pension and Other Postretirem90
Pension and Other Postretirement Benefits - Schedule of Fair Value of Plan Assets (Parenthetical) (Detail) - USD ($) | 12 Months Ended | |
Dec. 31, 2016 | Dec. 31, 2015 | |
Defined Benefit Plan Disclosure [Line Items] | ||
Amounts not included in funded status table | $ 2,859,000 | |
Minimum [Member] | ||
Defined Benefit Plan Disclosure [Line Items] | ||
Redemption request notice to prior period | 1 day | |
Impact fee on redemptions and subscriptions of $5 million or more | 5,000,000 | |
Maximum [Member] | ||
Defined Benefit Plan Disclosure [Line Items] | ||
Redemption request notice to prior period | 30 days | |
Qualified Retirement Plan [Member] | ||
Defined Benefit Plan Disclosure [Line Items] | ||
Amounts not included in funded status table | 2,803,000 | |
PBOP [Member] | ||
Defined Benefit Plan Disclosure [Line Items] | ||
Amounts not included in funded status table | $ 56,000 |
Stock-Based Compensation - Sche
Stock-Based Compensation - Schedule of Stock-Based Plan Compensation Expense, Including Cash Award (Detail) - USD ($) $ in Thousands | 12 Months Ended | ||
Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2014 | |
Disclosure of Compensation Related Costs, Share-based Payments [Abstract] | |||
Stock-based compensation plan expense, net of related tax benefits | $ 7,185 | $ 7,278 | $ 8,130 |
Stock-based compensation plan related tax benefits | $ 4,404 | $ 4,461 | $ 4,983 |
Stock-Based Compensation - Addi
Stock-Based Compensation - Additional Information (Detail) | 12 Months Ended | ||
Dec. 31, 2016USD ($) | Dec. 31, 2015$ / shares | Dec. 31, 2014$ / shares | |
Disclosure of Compensation Related Costs, Share-based Payments [Abstract] | |||
Options, maximum term, years | 10 years | ||
Cash received from exercise of stock options | $ 735,000 | ||
Tax benefit realized from exercise of stock options | $ 205,000 | ||
Percentage of restricted stock/units vested during first year | 0.40 | ||
Percentage of restricted stock/units vested during second and third years | 0.30 | ||
Weighted average grant date fair value of performance shares and restricted stock/units granted | $ / shares | $ 63.09 | $ 53.73 | |
Total compensation cost related to nonvested performance shares and restricted stock/units not yet recognized | $ 3,300,000 |
Stock-Based Compensation - Sc93
Stock-Based Compensation - Schedule of Stock Options Activity (Detail) - $ / shares shares in Thousands | 12 Months Ended | ||
Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2014 | |
Disclosure of Compensation Related Costs, Share-based Payments [Abstract] | |||
Number of options, Outstanding at the beginning of the year | 17 | 36 | 52 |
Number of options, Exercised during the year | (17) | (19) | (16) |
Number of options, Forfeited or expired during the year | 0 | 0 | 0 |
Number of options, Outstanding and exercisable at year end | 0 | 17 | 36 |
Weighted-average exercise price, Outstanding at the beginning of the year | $ 31.64 | $ 28.97 | $ 27.57 |
Weighted-average exercise price, Exercised during the year | 31.64 | 26.69 | 24.31 |
Weighted-average exercise price, Forfeited or expired during the year | $ 0 | 0 | 0 |
Weighted-average exercise price, Outstanding and exercisable at year end | $ 31.64 | $ 28.97 |
Stock-Based Compensation - Sc94
Stock-Based Compensation - Schedule of Aggregate Intrinsic Value of Outstanding and Exercisable Options (Detail) - USD ($) $ in Thousands | 12 Months Ended | ||
Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2014 | |
Disclosure of Compensation Related Costs, Share-based Payments [Abstract] | |||
Outstanding and exercisable | $ 0 | $ 394 | $ 1,194 |
Exercised | $ 554 | $ 590 | $ 451 |
Stock-Based Compensation - Summ
Stock-Based Compensation - Summary of Market Prices of Common Stock (Detail) - USD ($) | Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2014 |
Disclosure of Compensation Related Costs, Share-based Payments [Abstract] | |||
Market value of Company stock | $ 76.62 | $ 55.16 | $ 61.81 |
Stock-Based Compensation - Sc96
Stock-Based Compensation - Schedule of Nonvested Performance and Restricted Stock Unit Plans (Detail) - $ / shares shares in Thousands | 12 Months Ended | ||
Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2014 | |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | |||
Weighted-average grant date fair value, Granted | $ 63.09 | $ 53.73 | |
Performance Shares [Member] | |||
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | |||
Nonvested/unissued, Number of Units, at beginning of year | 197 | ||
Nonvested, Number of Units, Granted | 44 | ||
Nonvested, Number of Units, Dividends | 5 | ||
Nonvested, Number of Units, Forfeited or expired | 0 | ||
Nonvested, Number of Units, Vested and issued | (78) | ||
Nonvested/unissued, Number of Units, Ending balance | 168 | 197 | |
Weighted-average grant date fair value, Beginning balance | $ 50.63 | ||
Weighted-average grant date fair value, Granted | 59.05 | ||
Weighted-average grant date fair value, Dividends | 0 | ||
Weighted-average grant date fair value, Forfeited or expired | 0 | ||
Weighted-average grant date fair value, Vested and issued | 41.82 | ||
Weighted-average grant date fair value, Ending balance | $ 55.62 | $ 50.63 | |
Restricted Stock/Units [Member] | |||
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | |||
Nonvested/unissued, Number of Units, at beginning of year | 228 | ||
Nonvested, Number of Units, Granted | 73 | ||
Nonvested, Number of Units, Dividends | 6 | ||
Nonvested, Number of Units, Forfeited or expired | 0 | ||
Nonvested, Number of Units, Vested and issued | (45) | ||
Nonvested/unissued, Number of Units, Ending balance | 262 | 228 | |
Weighted-average grant date fair value, Beginning balance | $ 44.36 | ||
Weighted-average grant date fair value, Granted | 60.39 | ||
Weighted-average grant date fair value, Dividends | 0 | ||
Weighted-average grant date fair value, Forfeited or expired | 0 | ||
Weighted-average grant date fair value, Vested and issued | 51.98 | ||
Weighted-average grant date fair value, Ending balance | $ 46.41 | $ 44.36 |
Income Taxes - Summary of Incom
Income Taxes - Summary of Income Before Taxes and Noncontrolling Interest for Domestic and Foreign Operations (Detail) - USD ($) $ in Thousands | 12 Months Ended | ||
Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2014 | |
Income Tax [Line Items] | |||
Total income before income taxes | $ 231,523 | $ 219,332 | $ 219,521 |
Foreign [Member] | |||
Income Tax [Line Items] | |||
Total income before income taxes | 12,713 | (2,328) | (1,950) |
United States [Member] | |||
Income Tax [Line Items] | |||
Total income before income taxes | $ 218,810 | $ 221,660 | $ 221,471 |
Income Taxes - Summary of Inc98
Income Taxes - Summary of Income Tax Expense (Benefit) (Detail) - USD ($) $ in Thousands | 12 Months Ended | ||
Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2014 | |
Current: | |||
Federal | $ 541 | $ 21,321 | $ 1,739 |
State | 5,748 | 9,899 | 5,073 |
Foreign | 4,298 | 650 | 2,193 |
Income tax expense (benefit), Current | 10,587 | 31,870 | 9,005 |
Deferred: | |||
Federal | 68,270 | 51,132 | 71,439 |
State | 140 | (2,574) | 614 |
Foreign | (529) | (526) | (2,685) |
Total deferred income tax expense | 67,881 | 48,032 | 69,368 |
Total income tax expense | $ 78,468 | $ 79,902 | $ 78,373 |
Income Taxes - Significant Comp
Income Taxes - Significant Components of Deferred Income Tax Expense (Benefit) (Detail) - USD ($) $ in Thousands | 12 Months Ended | ||
Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2014 | |
Deferred federal and state: | |||
Total deferred federal and state | $ 68,719 | $ 48,893 | $ 70,229 |
Deferred ITC, net | (838) | (861) | (861) |
Total deferred income tax expense | 67,881 | 48,032 | 69,368 |
Property-related Items [Member] | |||
Deferred federal and state: | |||
Total deferred federal and state | 76,217 | 65,931 | 52,814 |
Purchased Gas Cost Adjustments [Member] | |||
Deferred federal and state: | |||
Total deferred federal and state | 361 | (32,993) | 15,049 |
Employee Benefits [Member] | |||
Deferred federal and state: | |||
Total deferred federal and state | (1,327) | 623 | 109 |
All Other Deferred [Member] | |||
Deferred federal and state: | |||
Total deferred federal and state | $ (6,532) | $ 15,332 | $ 2,257 |
Income Taxes - Reconciliation o
Income Taxes - Reconciliation of U.S Federal Statutory Rate to Consolidated Effective Tax Rate (Detail) | 12 Months Ended | ||
Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2014 | |
Income Tax Disclosure [Abstract] | |||
U.S. federal statutory income tax rate | 35.00% | 35.00% | 35.00% |
Net state taxes | 1.40% | 1.80% | 1.90% |
Property-related items | 0.00% | 0.10% | 0.10% |
Tax credits | (0.40%) | (0.40%) | (0.50%) |
Company owned life insurance | (1.20%) | 0.10% | (1.00%) |
All other differences | (0.90%) | (0.20%) | 0.20% |
Consolidated effective income tax rate | 33.90% | 36.40% | 35.70% |
Income Taxes - Deferred Tax Ass
Income Taxes - Deferred Tax Assets and Liabilities (Detail) - USD ($) $ in Thousands | Dec. 31, 2016 | Dec. 31, 2015 |
Deferred tax assets: | ||
Deferred income taxes for future amortization of ITC | $ 1,094 | $ 1,614 |
Employee benefits | 38,231 | 36,923 |
Alternative minimum tax credit | 4,827 | 4,809 |
Net operating losses and credits | 1,204 | 868 |
Interest rate swap | 6,080 | 7,351 |
Other | 18,415 | 24,636 |
Valuation allowance | (495) | (499) |
Deferred tax assets, total | 69,356 | 75,702 |
Deferred tax liabilities: | ||
Property-related items, including accelerated depreciation | 872,136 | 794,850 |
Regulatory balancing accounts | 1,104 | 743 |
Unamortized ITC | 1,710 | 2,549 |
Debt-related costs | 5,712 | 5,497 |
Intangibles | 8,803 | 9,547 |
Other | 19,256 | 31,533 |
Deferred tax liabilities, total | 908,721 | 844,719 |
Net noncurrent deferred tax liabilities | $ 839,365 | $ 769,017 |
Income Taxes - Additional Infor
Income Taxes - Additional Information (Detail) - USD ($) | 12 Months Ended | ||
Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2014 | |
Income Tax Disclosure [Line Items] | |||
Undistributed foreign earnings | $ 5,000,000 | ||
Unrecognized tax benefits that, if recognized, would affect the effective tax rate | 935,000 | ||
Significant increases or decreases in unrecognized tax benefit within the next 12 months | 0 | ||
Tax-related interest income | $ 0 | $ 0 | $ 0 |
Minimum [Member] | |||
Income Tax Disclosure [Line Items] | |||
Amount of benefit being recognized in financial statements upon ultimate settlement, Percentage | 50.00% | ||
United States [Member] | |||
Income Tax Disclosure [Line Items] | |||
Federal net capital loss carryforward | $ 278,000 | ||
Net capital loss carryforward expiration year | 2,017 | ||
Canada [Member] | |||
Income Tax Disclosure [Line Items] | |||
Federal net operating loss carryforward | $ 4,500,000 | ||
Net operating loss carryforward expiration year | 2,032 |
Income Taxes - Reconciliatio103
Income Taxes - Reconciliation of Unrecognized Tax Benefits (Detail) - USD ($) $ in Thousands | 12 Months Ended | |
Dec. 31, 2016 | Dec. 31, 2015 | |
Income Tax Disclosure [Abstract] | ||
Unrecognized tax benefits at beginning of year | $ 296 | $ 305 |
Gross increases - tax positions in prior period | 897 | 0 |
Gross decreases - tax positions in prior period | 0 | (9) |
Gross increases - current period tax positions | 38 | 0 |
Gross decreases - current period tax positions | 0 | 0 |
Settlements | 0 | 0 |
Lapse in statute of limitations | 0 | 0 |
Unrecognized tax benefits at end of year | $ 1,231 | $ 296 |
Derivatives and Fair Value M104
Derivatives and Fair Value Measurements - Additional Information (Detail) - USD ($) | 12 Months Ended | ||
Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2014 | |
Derivative [Line Items] | |||
Gains (losses) recognized in income or other comprehensive income for derivative designated cash flow hedges | $ 2,075,000 | $ 2,073,000 | $ 2,073,000 |
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 | ||
Minimum [Member] | |||
Derivative [Line Items] | |||
Maturities of natural gas swaps | Jan. 31, 2017 | ||
Maximum [Member] | |||
Derivative [Line Items] | |||
Maturities of natural gas swaps | Mar. 31, 2019 | ||
Arizona [Member] | |||
Derivative [Line Items] | |||
Natural gas portfolios, maximum % rate | 25.00% | ||
California [Member] | |||
Derivative [Line Items] | |||
Natural gas portfolios, maximum % rate | 25.00% |
Derivatives and Fair Value M105
Derivatives and Fair Value Measurements - Notional Amounts under Swaps Contracts (Detail) - MMBTU | Dec. 31, 2016 | Dec. 31, 2015 |
Offsetting [Abstract] | ||
Contract notional amounts | 10,543,000 | 7,407,000 |
Derivatives and Fair Value M106
Derivatives and Fair Value Measurements - Amount of Gain or Losses Recognized in Income on Derivatives (Detail) - USD ($) $ in Thousands | 12 Months Ended | ||
Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2014 | |
Derivative Instruments, Gain (Loss) [Line Items] | |||
Amount of gain or (loss) recognized in income on derivative | $ 0 | $ 0 | $ 0 |
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 | 5,006 | (7,598) | (2,363) |
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 | $ (5,006) | $ 7,598 | $ 2,363 |
Derivatives and Fair Value M107
Derivatives and Fair Value Measurements - Fair Values of Swaps in Consolidated Balance Sheets (Detail) - USD ($) $ in Thousands | Dec. 31, 2016 | Dec. 31, 2015 |
Derivatives, Fair Value [Line Items] | ||
Asset derivatives not designated as hedging instruments | $ 4,450 | $ 4 |
Liability derivatives not designated as hedging instruments | (73) | (5,490) |
Net total not designated as hedging instruments | 4,377 | (5,486) |
Swaps [Member] | Deferred Charges and Other Assets [Member] | ||
Derivatives, Fair Value [Line Items] | ||
Asset derivatives not designated as hedging instruments | 899 | |
Liability derivatives not designated as hedging instruments | (54) | |
Net total not designated as hedging instruments | 845 | |
Swaps [Member] | Prepaids and Other Current Assets [Member] | ||
Derivatives, Fair Value [Line Items] | ||
Asset derivatives not designated as hedging instruments | 3,551 | |
Liability derivatives not designated as hedging instruments | (19) | |
Net total not designated as hedging instruments | $ 3,532 | |
Swaps [Member] | Other Current Liabilities [Member] | ||
Derivatives, Fair Value [Line Items] | ||
Asset derivatives not designated as hedging instruments | 0 | |
Liability derivatives not designated as hedging instruments | (4,267) | |
Net total not designated as hedging instruments | (4,267) | |
Swaps [Member] | Other Deferred Credits [Member] | ||
Derivatives, Fair Value [Line Items] | ||
Asset derivatives not designated as hedging instruments | 4 | |
Liability derivatives not designated as hedging instruments | (1,223) | |
Net total not designated as hedging instruments | $ (1,219) |
Derivatives and Fair Value M108
Derivatives and Fair Value Measurements - Paid to and Received from Counterparties for Settlements of Matured Swaps (Detail) - USD ($) $ in Thousands | 12 Months Ended | ||
Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2014 | |
Derivative Instruments and Hedging Activities Disclosure [Abstract] | |||
Paid to counterparties | $ 5,583 | $ 7,537 | $ 829 |
Received from counterparties | $ 726 | $ 0 | $ 4,713 |
Derivatives and Fair Value M109
Derivatives and Fair Value Measurements - Regulatory Assets/Liabilities Offsetting Derivatives at Fair Value in Condensed Consolidated Balance Sheets (Detail) - Swaps [Member] - USD ($) $ in Thousands | Dec. 31, 2016 | Dec. 31, 2015 |
Other Deferred Credits [Member] | ||
Derivatives, Fair Value [Line Items] | ||
Net Total | $ (845) | |
Other Current Liabilities [Member] | ||
Derivatives, Fair Value [Line Items] | ||
Net Total | $ (3,532) | |
Prepaids and Other Current Assets [Member] | ||
Derivatives, Fair Value [Line Items] | ||
Net Total | $ 4,267 | |
Deferred Charges and Other Assets [Member] | ||
Derivatives, Fair Value [Line Items] | ||
Net Total | $ 1,219 |
Derivatives and Fair Value M110
Derivatives and Fair Value Measurements - Significant Other Observable Inputs (Detail) - Level 2 - Significant Other Observable Inputs [Member] - Swaps [Member] - USD ($) $ in Thousands | Dec. 31, 2016 | Dec. 31, 2015 |
Derivatives, Fair Value [Line Items] | ||
Net Assets (Liabilities) | $ 4,377 | $ (5,486) |
Prepaids and Other Current Assets [Member] | ||
Derivatives, Fair Value [Line Items] | ||
Derivative Assets | 3,532 | 0 |
Deferred Charges and Other Assets [Member] | ||
Derivatives, Fair Value [Line Items] | ||
Derivative Assets | 845 | 0 |
Other Current Liabilities [Member] | ||
Derivatives, Fair Value [Line Items] | ||
Derivative Liabilities | 0 | (4,267) |
Other Deferred Credits [Member] | ||
Derivatives, Fair Value [Line Items] | ||
Derivative Liabilities | $ 0 | $ (1,219) |
Segment Information - Additiona
Segment Information - Additional Information (Detail) | 12 Months Ended |
Dec. 31, 2016 | |
Net Assets, Geographic Area [Member] | Geographic Concentration Risk [Member] | United States [Member] | Minimum [Member] | |
Segment Reporting Information [Line Items] | |
Long-lived assets | 99.00% |
Segment Information - Accounts
Segment Information - Accounts Receivable for Services (Detail) - USD ($) $ in Thousands | Dec. 31, 2016 | Dec. 31, 2015 |
Centuri Construction Group Inc [Member] | ||
Segment Reporting Information [Line Items] | ||
Accounts receivable for Centuri services | $ 10,585 | $ 10,006 |
Segment Information - Schedule
Segment Information - Schedule of Revenues by Geographic Area (Detail) - USD ($) $ in Thousands | 3 Months Ended | 12 Months Ended | |||||||||||||
Dec. 31, 2016 | Sep. 30, 2016 | Jun. 30, 2016 | Mar. 31, 2016 | Dec. 31, 2015 | Sep. 30, 2015 | Jun. 30, 2015 | Mar. 31, 2015 | Dec. 31, 2014 | Sep. 30, 2014 | Jun. 30, 2014 | Mar. 31, 2014 | Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2014 | |
Segment Reporting Information [Line Items] | |||||||||||||||
Total Revenues | $ 641,525 | $ 539,969 | $ 547,748 | $ 731,248 | $ 685,405 | $ 505,396 | $ 538,604 | $ 734,220 | $ 627,683 | $ 432,475 | $ 453,153 | $ 608,396 | $ 2,460,490 | $ 2,463,625 | $ 2,121,707 |
United States [Member] | |||||||||||||||
Segment Reporting Information [Line Items] | |||||||||||||||
Total Revenues | 2,256,600 | 2,289,133 | 2,069,513 | ||||||||||||
Canada [Member] | |||||||||||||||
Segment Reporting Information [Line Items] | |||||||||||||||
Total Revenues | $ 203,890 | $ 174,492 | $ 52,194 |
Segment Information - Schedu114
Segment Information - Schedule of Segment Reporting Information (Detail) - USD ($) $ in Thousands | 3 Months Ended | 12 Months Ended | |||||||||||||
Dec. 31, 2016 | Sep. 30, 2016 | Jun. 30, 2016 | Mar. 31, 2016 | Dec. 31, 2015 | Sep. 30, 2015 | Jun. 30, 2015 | Mar. 31, 2015 | Dec. 31, 2014 | Sep. 30, 2014 | Jun. 30, 2014 | Mar. 31, 2014 | Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2014 | |
Segment Reporting Information [Line Items] | |||||||||||||||
Total operating revenues | $ 641,525 | $ 539,969 | $ 547,748 | $ 731,248 | $ 685,405 | $ 505,396 | $ 538,604 | $ 734,220 | $ 627,683 | $ 432,475 | $ 453,153 | $ 608,396 | $ 2,460,490 | $ 2,463,625 | $ 2,121,707 |
Interest revenue | 1,849 | 2,173 | 2,602 | ||||||||||||
Interest expense | 73,660 | 71,879 | 72,069 | ||||||||||||
Depreciation and amortization | 289,132 | 270,111 | 253,027 | ||||||||||||
Income tax expense | 78,468 | 79,902 | 78,373 | ||||||||||||
Segment net income | 65,180 | $ 2,472 | $ 8,943 | $ 75,446 | 66,119 | $ (4,734) | $ 4,949 | $ 71,983 | 58,746 | $ 1,970 | $ 9,627 | $ 70,783 | 152,041 | 138,317 | 141,126 |
Segment assets | 5,581,126 | 5,358,685 | 5,208,297 | 5,581,126 | 5,358,685 | 5,208,297 | |||||||||
Capital expenditures | 529,531 | 488,000 | 396,898 | ||||||||||||
Revenues from unaffiliated customers [Member] | |||||||||||||||
Segment Reporting Information [Line Items] | |||||||||||||||
Revenues | 2,362,369 | 2,359,509 | 2,029,519 | ||||||||||||
Intersegment sales [Member] | |||||||||||||||
Segment Reporting Information [Line Items] | |||||||||||||||
Revenues | 98,121 | 104,116 | 92,188 | ||||||||||||
Natural Gas Operations [Member] | |||||||||||||||
Segment Reporting Information [Line Items] | |||||||||||||||
Total operating revenues | 1,321,412 | 1,454,639 | 1,382,087 | ||||||||||||
Interest revenue | 1,848 | 1,754 | 2,596 | ||||||||||||
Interest expense | 66,997 | 64,095 | 68,299 | ||||||||||||
Depreciation and amortization | 233,463 | 213,455 | 204,144 | ||||||||||||
Income tax expense | 58,584 | 61,355 | 63,597 | ||||||||||||
Segment net income | 119,423 | 111,625 | 116,872 | ||||||||||||
Segment assets | 5,001,756 | 4,822,845 | 4,652,307 | 5,001,756 | 4,822,845 | 4,652,307 | |||||||||
Capital expenditures | 457,120 | 438,289 | 350,025 | ||||||||||||
Natural Gas Operations [Member] | Revenues from unaffiliated customers [Member] | |||||||||||||||
Segment Reporting Information [Line Items] | |||||||||||||||
Revenues | 1,321,412 | 1,454,639 | 1,382,087 | ||||||||||||
Natural Gas Operations [Member] | Intersegment sales [Member] | |||||||||||||||
Segment Reporting Information [Line Items] | |||||||||||||||
Revenues | 0 | 0 | 0 | ||||||||||||
Construction Services [Member] | |||||||||||||||
Segment Reporting Information [Line Items] | |||||||||||||||
Total operating revenues | 1,139,078 | 1,008,986 | 739,620 | ||||||||||||
Interest revenue | 1 | 419 | 6 | ||||||||||||
Interest expense | 6,663 | 7,784 | 3,770 | ||||||||||||
Depreciation and amortization | 55,669 | 56,656 | 48,883 | ||||||||||||
Income tax expense | 19,884 | 18,547 | 14,776 | ||||||||||||
Segment net income | 32,618 | 26,692 | 24,254 | ||||||||||||
Segment assets | $ 579,370 | $ 535,840 | 566,589 | 579,370 | 535,840 | 566,589 | |||||||||
Capital expenditures | 72,411 | 49,711 | 46,873 | ||||||||||||
Construction Services [Member] | Revenues from unaffiliated customers [Member] | |||||||||||||||
Segment Reporting Information [Line Items] | |||||||||||||||
Revenues | 1,040,957 | 904,870 | 647,432 | ||||||||||||
Construction Services [Member] | Intersegment sales [Member] | |||||||||||||||
Segment Reporting Information [Line Items] | |||||||||||||||
Revenues | $ 98,121 | $ 104,116 | 92,188 | ||||||||||||
Adjustments [Member] | |||||||||||||||
Segment Reporting Information [Line Items] | |||||||||||||||
Segment assets | $ (10,599) | $ (10,599) |
Segment Information - Schedu115
Segment Information - Schedule of Segment Reporting Information (Parenthetical) (Detail) - USD ($) $ in Thousands | 12 Months Ended | ||
Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2014 | |
Segment Reporting Information [Line Items] | |||
Long-term deferred tax benefit | $ 67,881 | $ 48,032 | $ 69,368 |
Natural Gas Operations [Member] | |||
Segment Reporting Information [Line Items] | |||
Deferred income tax liability | 4,500 | ||
Construction Services [Member] | |||
Segment Reporting Information [Line Items] | |||
Income tax payable netted | 3,300 | ||
Deferred income tax liability | 1,400 | ||
Long-term deferred tax benefit | $ 1,400 |
Quarterly Financial Data - Sche
Quarterly Financial Data - Schedule of Quarterly Financial Information (Detail) - USD ($) $ / shares in Units, $ in Thousands | 3 Months Ended | 12 Months Ended | |||||||||||||
Dec. 31, 2016 | Sep. 30, 2016 | Jun. 30, 2016 | Mar. 31, 2016 | Dec. 31, 2015 | Sep. 30, 2015 | Jun. 30, 2015 | Mar. 31, 2015 | Dec. 31, 2014 | Sep. 30, 2014 | Jun. 30, 2014 | Mar. 31, 2014 | Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2014 | |
Quarterly Financial Information Disclosure [Abstract] | |||||||||||||||
Operating revenues | $ 641,525 | $ 539,969 | $ 547,748 | $ 731,248 | $ 685,405 | $ 505,396 | $ 538,604 | $ 734,220 | $ 627,683 | $ 432,475 | $ 453,153 | $ 608,396 | $ 2,460,490 | $ 2,463,625 | $ 2,121,707 |
Operating income | 117,963 | 15,539 | 28,116 | 134,096 | 117,586 | 16,143 | 25,047 | 129,556 | 112,373 | 18,290 | 26,755 | 127,065 | 295,714 | 288,332 | 284,483 |
Net income (loss) | 65,694 | 2,907 | 9,099 | 75,355 | 66,698 | (4,210) | 5,063 | 71,879 | 58,897 | 1,927 | 9,627 | 70,697 | 153,055 | 139,430 | 141,148 |
Net income (loss) attributable to Southwest Gas Corporation | $ 65,180 | $ 2,472 | $ 8,943 | $ 75,446 | $ 66,119 | $ (4,734) | $ 4,949 | $ 71,983 | $ 58,746 | $ 1,970 | $ 9,627 | $ 70,783 | $ 152,041 | $ 138,317 | $ 141,126 |
Basic earnings (loss) per common share | $ 1.37 | $ 0.05 | $ 0.19 | $ 1.59 | $ 1.40 | $ (0.10) | $ 0.11 | $ 1.54 | $ 1.26 | $ 0.04 | $ 0.21 | $ 1.52 | $ 3.20 | $ 2.94 | $ 3.04 |
Diluted earnings (loss) per common share | $ 1.36 | $ 0.05 | $ 0.19 | $ 1.58 | $ 1.38 | $ (0.10) | $ 0.10 | $ 1.53 | $ 1.25 | $ 0.04 | $ 0.21 | $ 1.51 | $ 3.18 | $ 2.92 | $ 3.01 |
Construction Services Noncon117
Construction Services Noncontrolling Interests - Additional Information (Detail) | 1 Months Ended | 12 Months Ended |
Oct. 31, 2014 | Dec. 31, 2016 | |
Principal Previous Owners [Member] | Link-Line and WS Nicholls [Member] | ||
Noncontrolling Interest [Line Items] | ||
Equity interest percentage | 10.00% | |
Description of equity interest | Associated with the agreement reached in conjunction with the acquisition of the Canadian construction businesses in October 2014, the previous owners of the acquired companies initially retained an approximate 10% equity interest in the Canadian-specific businesses, and special dividend rights which entitled the sellers, as holders, to dividends equal to 3.4% of dividends paid at the level of Centuri, and subject to certain conditions, such interests could become exchangeable for a 3.4% equity interest in Centuri. In consideration of the underlying exchange rights of the original agreement, earnings attribution by Centuri to the previous owners also occurred in an amount equivalent to 3.4% of Centuri earnings since October 2014. During the third quarter of 2015, the sellers formally exercised their exchange rights under the terms of the original agreement. No new rights were conveyed to the noncontrolling parties as a result of the exchange and no new consideration was involved. The previous owners are currently eligible to exit their investment retained by requiring the purchase of a portion of their interest and in incremental amounts annually. The shares subject to the election cumulate (if earlier elections are not made) such that 100% of their interest retained is subject to the election beginning in July 2022. | |
Equity interest dividend rights, percentage of dividends paid by Centuri | 3.40% | |
Principal Previous Owners [Member] | Link-Line and WS Nicholls [Member] | Construction Services [Member] | ||
Noncontrolling Interest [Line Items] | ||
Equity interest exchangeable percentage in Centuri | 3.40% | |
Percentage of earnings attribution by Centuri to previous owners | 3.40% | |
Principal Previous Owners [Member] | Link-Line and WS Nicholls [Member] | Construction Services [Member] | Maximum [Member] | ||
Noncontrolling Interest [Line Items] | ||
Percentage of retained interest may elect to sell to centuri | 100.00% | |
IntelliChoice Energy, LLC [Member] | ||
Noncontrolling Interest [Line Items] | ||
Subsidiaries holding interest percentage | 65.00% |
Construction Services Noncon118
Construction Services Noncontrolling Interests - Summary of Redeemable Noncontrolling Interest (Detail) - USD ($) $ in Thousands | 12 Months Ended | ||
Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2014 | |
Redeemable Noncontrolling Interest [Line Items] | |||
Balance, December 31, 2015 | $ 16,108 | ||
Balance, December 31, 2016 | 22,590 | $ 16,108 | |
Redeemable Noncontrolling Interest (Temporary Equity) [Member] | |||
Redeemable Noncontrolling Interest [Line Items] | |||
Balance, December 31, 2015 | 16,108 | 20,042 | |
Net Income (loss) attributable to redeemable noncontrolling interest | 1,148 | 939 | $ 151 |
Foreign currency exchange translation adjustment | 5 | (66) | (22) |
Centuri distribution to redeemable noncontrolling interest | (439) | (99) | |
Adjustment to redemption value | 5,768 | ||
Balance, December 31, 2016 | $ 22,590 | $ 16,108 | $ 20,042 |