CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended		12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
CASH FLOW FROM OPERATING ACTIVITIES:
Net income (loss)	$ 124,741	$ 112,176	$ 194,217	$ 208,572
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	223,251	185,941	286,522	247,803
Deferred income taxes	46,099	36,210	60,930	50,190
Changes in current assets and liabilities:
Accounts receivable, net of allowances	(19,615)	(1,659)	(33,818)	(27,276)
Accrued utility revenue	41,400	43,600	(1,200)	(500)
Deferred purchased gas costs	(36,608)	100,763	(54,797)	84,282
Accounts payable	(46,079)	(48,618)	14,317	(1,886)
Accrued taxes	(2,841)	(9,840)	(4,956)	(12,417)
Other current assets and liabilities	74,048	1,245	18,730	(50,002)
Gains on sale	(3,157)	(997)	(3,863)	(3,741)
Changes in undistributed stock compensation	6,067	4,686	7,492	6,375
Equity AFUDC	(3,179)	(1,034)	(5,772)	(1,253)
Changes in other assets and deferred charges	(15,855)	(10,497)	(11,096)	(18,296)
Changes in other liabilities and deferred credits	(9,786)	(4,583)	33,243	(3,747)
Net cash provided by operating activities	378,486	407,393	499,949	478,104
CASH FLOW FROM INVESTING ACTIVITIES:
Construction expenditures and property additions	(719,386)	(560,165)	(925,135)	(733,816)
Acquisition of businesses, net of cash acquired	(19,533)	(4,209)	(266,697)	(98,413)
Changes in customer advances	15,049	11,051	17,461	13,325
Miscellaneous inflows	12,862	3,827	13,376	11,312
Net cash used in investing activities	(711,008)	(549,496)	(1,160,995)	(807,592)
CASH FLOW FROM FINANCING ACTIVITIES:
Issuance of common stock, net	129,341	92,234	391,509	121,826
Dividends paid	(86,345)	(74,535)	(112,050)	(98,162)
Issuance of long-term debt, net	482,614	480,993	566,793	783,748
Retirement of long-term debt	(127,175)	(143,757)	(221,176)	(382,486)
Change in short-term debt	(122,000)	(183,000)	(1,500)	(79,000)
Principal payments on finance lease obligations	(161)	(422)	(387)	(606)
Withholding remittance - share-based compensation	(1,858)	(2,880)	(2,088)	(2,880)
Other	1,167	(1,121)	(456)	(3,091)
Net cash provided by financing activities	275,583	167,512	620,645	339,349
Effects of currency translation on cash and cash equivalents	58	139	(289)	157
Change in cash and cash equivalents	(56,881)	25,548	(40,690)	10,018
Cash and cash equivalents at beginning of period	85,361	43,622	69,170	59,152
Cash and cash equivalents at end of period	28,480	69,170	28,480	69,170
Supplemental information:
Interest paid, net of amounts capitalized	62,165	49,568	99,159	75,740
Income taxes paid (received)	371	18,261	(16,669)	20,247
Southwest Gas Corporation
CASH FLOW FROM OPERATING ACTIVITIES:
Net income (loss)	86,746	79,301	146,287	153,683
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	159,327	145,549	205,594	193,828
Deferred income taxes	35,899	33,239	45,659	55,787
Changes in current assets and liabilities:
Accounts receivable, net of allowances	66,527	49,654	(3,436)	(2,066)
Accrued utility revenue	41,400	43,600	(1,200)	(500)
Deferred purchased gas costs	(36,608)	100,763	(54,797)	84,282
Accounts payable	(77,311)	(53,217)	(686)	(2,700)
Accrued taxes	(4,419)	(16,026)	(7,125)	(9,735)
Other current assets and liabilities	87,869	(35,154)	31,579	(81,333)
Changes in undistributed stock compensation	4,710	4,269	5,796	5,558
Equity AFUDC	(3,179)	(1,034)	(5,772)	(1,253)
Changes in other assets and deferred charges	(21,098)	(11,025)	(17,122)	(19,082)
Changes in other liabilities and deferred credits	(10,357)	7,550	19,762	8,208
Net cash provided by operating activities	329,506	347,469	364,539	384,677
CASH FLOW FROM INVESTING ACTIVITIES:
Construction expenditures and property additions	(587,405)	(486,037)	(784,237)	(651,022)
Changes in customer advances	15,049	11,051	17,461	13,325
Miscellaneous inflows	(51)	1,316	(1,353)	1,650
Net cash used in investing activities	(572,407)	(473,670)	(768,129)	(636,047)
CASH FLOW FROM FINANCING ACTIVITIES:
Contributions from parent	126,186	90,644	149,091	120,344
Dividends paid	(71,000)	(65,000)	(93,000)	(86,000)
Issuance of long-term debt, net	297,222	297,495	297,222	297,495
Change in short-term debt	(122,000)	(182,000)	21,000	(74,000)
Withholding remittance - share-based compensation	(1,857)	(2,880)	(2,087)	(2,880)
Other	(801)	(939)	(890)	(991)
Net cash provided by financing activities	227,750	137,320	371,336	253,968
Change in cash and cash equivalents	(15,151)	11,119	(32,254)	2,598
Cash and cash equivalents at beginning of period	31,962	37,946	49,065	46,467
Cash and cash equivalents at end of period	16,811	49,065	16,811	49,065
Supplemental information:
Interest paid, net of amounts capitalized	51,720	42,986	82,539	67,025
Income taxes paid (received)	$ (22)	$ 11,286	$ (17,164)	$ 3,428