CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended		12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
CASH FLOW FROM OPERATING ACTIVITIES:
Net income	$ 112,176	$ 97,546	$ 208,572	$ 163,240
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	185,941	189,089	247,803	260,457
Deferred income taxes	36,210	49,409	50,190	74,439
Changes in current assets and liabilities:
Accounts receivable, net of allowances	(1,659)	(15,330)	(27,276)	(13,765)
Accrued utility revenue	43,600	42,100	(500)	(1,100)
Deferred purchased gas costs	100,763	(79,127)	84,282	(114,658)
Accounts payable	(48,618)	(26,771)	(1,886)	19,866
Accrued taxes	(9,840)	4,689	(12,417)	38,084
Other current assets and liabilities	1,245	43,044	(50,002)	3,590
Gains on sale	(997)	(1,452)	(3,741)	(4,483)
Changes in undistributed stock compensation	4,686	9,199	6,375	10,308
AFUDC	(1,034)	(2,077)	(1,253)	(2,473)
Changes in other assets and deferred charges	(10,497)	(14,470)	(18,296)	(1,436)
Changes in other liabilities and deferred credits	(4,583)	3,395	(3,747)	(10,239)
Net cash provided by operating activities	407,393	299,244	478,104	421,830
CASH FLOW FROM INVESTING ACTIVITIES:
Construction expenditures and property additions	(560,165)	(449,998)	(733,816)	(575,141)
Acquisition of businesses, net of cash acquired	(4,209)	0	(98,413)	0
Changes in customer advances	11,051	(1,951)	13,325	504
Miscellaneous inflows	3,827	9,160	11,312	14,234
Net cash used in investing activities	(549,496)	(442,789)	(807,592)	(560,403)
CASH FLOW FROM FINANCING ACTIVITIES:
Issuance of common stock, net	92,234	11,563	121,826	11,505
Dividends paid	(74,535)	(68,503)	(98,162)	(89,870)
Centuri distribution to redeemable noncontrolling interest	0	(204)	0	(544)
Issuance of long-term debt, net	480,993	104,308	783,748	119,308
Retirement of long-term debt	(143,757)	(100,240)	(382,486)	(159,162)
Change in credit facility and commercial paper	0	145,000	0	150,000
Change in short-term debt	(183,000)	110,500	(79,000)	110,500
Principal payments on capital lease obligations	(422)	(796)	(606)	(1,025)
Redemption of Centuri shares from noncontrolling parties	0	(23,000)	0	(23,000)
Withholding remittance - share-based compensation	(2,880)	(3,176)	(2,880)	(3,176)
Other	(1,121)	(1,104)	(3,091)	(2,068)
Net cash provided by financing activities	167,512	174,348	339,349	112,468
Effects of currency translation on cash and cash equivalents	139	283	157	103
Change in cash and cash equivalents	25,548	31,086	10,018	(26,002)
Cash and cash equivalents at beginning of period	43,622	28,066	59,152	85,154
Cash and cash equivalents at end of period	69,170	59,152	69,170	59,152
Supplemental information:
Interest paid, net of amounts capitalized, continuing operations	49,568	45,771	75,740	66,077
Income taxes paid (received)	18,261	3,687	20,247	(21,875)
Southwest Gas Corporation
CASH FLOW FROM OPERATING ACTIVITIES:
Net income	79,301	82,436	153,683	148,130
Income from discontinued operations	0	0	0	13,807
Income from continuing operations	79,301	82,436	153,683	134,323
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	145,549	153,643	193,828	212,693
Deferred income taxes	33,239	44,621	55,787	72,627
Changes in current assets and liabilities:
Accounts receivable, net of allowances	49,654	43,818	(2,066)	(7,131)
Accrued utility revenue	43,600	42,100	(500)	(1,100)
Deferred purchased gas costs	100,763	(79,127)	84,282	(114,658)
Accounts payable	(53,217)	(45,972)	(2,700)	17,271
Accrued taxes	(16,026)	4,092	(9,735)	29,143
Other current assets and liabilities	(35,154)	32,453	(81,333)	(224)
Changes in undistributed stock compensation	4,269	7,999	5,558	9,108
AFUDC	(1,034)	(2,077)	(1,253)	(2,473)
Changes in other assets and deferred charges	(11,025)	(14,861)	(19,082)	(1,914)
Changes in other liabilities and deferred credits	7,550	2,883	8,208	(10,751)
Net cash provided by operating activities, continuing operations	347,469	272,008	384,677	336,914
CASH FLOW FROM INVESTING ACTIVITIES:
Construction expenditures and property additions	(486,037)	(395,463)	(651,022)	(514,661)
Changes in customer advances	11,051	(1,951)	13,325	504
Miscellaneous inflows	1,316	2,407	1,650	2,925
Dividends received	0	0	0	9,660
Net cash used in investing activities, continuing operations	(473,670)	(395,007)	(636,047)	(501,572)
CASH FLOW FROM FINANCING ACTIVITIES:
Issuance of common stock, net	0	0	0	(58)
Contributions from parent	90,644	11,659	120,344	11,659
Dividends paid	(65,000)	(60,497)	(86,000)	(81,864)
Issuance of long-term debt, net	297,495	0	297,495	0
Retirement of long-term debt	0	(25,000)	0	(25,000)
Change in credit facility and commercial paper	0	145,000	0	150,000
Change in short-term debt	(182,000)	83,000	(74,000)	83,000
Withholding remittance - share-based compensation	(2,880)	(3,176)	(2,880)	(3,176)
Other	(939)	(544)	(991)	(1,508)
Net cash provided by financing activities, continuing operations	137,320	150,442	253,968	133,053
Net cash provided by discontinued operating activities	0	0	0	57,680
Net cash used in discontinued investing activities	0	0	0	(11,049)
Net cash used in discontinued financing activities	0	0	0	(44,491)
Effects of currency translation on cash and cash equivalents	0	0	0	(180)
Change in cash and cash equivalents	11,119	27,443	2,598	(29,645)
Change in cash and cash equivalents of discontinued operations included in discontinued operations construction services assets	0	0	0	(1,960)
Change in cash and cash equivalents of continuing operations	11,119	27,443	2,598	(31,605)
Cash and cash equivalents at beginning of period	37,946	19,024	46,467	78,072
Cash and cash equivalents at end of period	49,065	46,467	49,065	46,467
Supplemental information:
Income taxes paid (received)	11,286	4	3,428	(27,952)
Interest paid, net of amounts capitalized	$ 42,986	$ 40,751	$ 67,025	$ 59,448