Long-Term Debt (Tables)

12 Months Ended

Dec. 31, 2018

Debt Disclosure [Abstract]

Schedule of Carrying Amounts and Estimated Fair Values of Long-Term Debt

The Centuri secured revolving credit and term loan facility and Centuri other debt obligations are categorized as Level 3, based on significant unobservable inputs to their fair values. Because 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. The fair value hierarchy is described in Note 1 - Background, Organization, and Summary of Significant Accounting Policies.

	December 31, 2018					December 31, 2017
	Carrying Amount			Market Value		Carrying Amount			Market Value
(Thousands of dollars)
Southwest Gas Corporation:
Debentures:
Notes, 4.45%, due 2020	$	125,000		$	126,213	$	125,000		$	129,273
Notes, 6.1%, due 2041	125,000			150,728		125,000			158,304
Notes, 3.875%, due 2022	250,000			254,195		250,000			256,163
Notes, 4.875%, due 2043	250,000			268,985		250,000			283,243
Notes, 3.8%, due 2046	300,000			267,030		300,000			302,970
Notes, 3.7%, due 2028	300,000			298,926		—			—
8% Series, due 2026	75,000			93,827		75,000			96,063
Medium-term notes, 7.78% series, due 2022	25,000			27,497		25,000			28,714
Medium-term notes, 7.92% series, due 2027	25,000			30,016		25,000			31,542
Medium-term notes, 6.76% series, due 2027	7,500			8,651		7,500			8,882
Unamortized discount and debt issuance costs	(11,807		)			(9,350		)
	1,470,693					1,173,150
Revolving credit facility and commercial paper	150,000			150,000		150,000			150,000
Industrial development revenue bonds:
Variable-rate bonds:
Tax-exempt Series A, due 2028	50,000			50,000		50,000			50,000
2003 Series A, due 2038	50,000			50,000		50,000			50,000
2008 Series A, due 2038	50,000			50,000		50,000			50,000
2009 Series A, due 2039	50,000			50,000		50,000			50,000
Unamortized discount and debt issuance costs	(2,024		)			(2,119		)
	197,976					197,881
Less: current maturities	—					—
Long-term debt, less current maturities – Southwest Gas Corporation	$	1,818,669				$	1,521,031
Centuri:
Centuri term loan facility	$	255,959		260,135		$	199,578		207,588
Unamortized debt issuance costs	(1,414		)			(1,111		)
	254,545					198,467
Centuri secured revolving credit facility	—			—		56,472			56,525
Centuri other debt obligations	67,104			67,053		47,952			48,183
Less: current maturities	(33,060		)			(25,346		)
Long-term debt, less current maturities – Centuri	$	288,589				$	277,545
Consolidated Southwest Gas Holdings, Inc.:
Southwest Gas Corporation long-term debt	$	1,818,669				$	1,521,031
Centuri long-term debt	321,649					302,891
Less: current maturities	(33,060		)			(25,346		)
Long-term debt, less current maturities – Southwest Gas Holdings, Inc.	$	2,107,258				$	1,798,576

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, 2018		December 31, 2017
2003 Series A	2.61	%	2.44	%
2008 Series A	2.52	%	2.59	%
2009 Series A	2.51	%	2.40	%
Tax-exempt Series A	2.53	%	2.56	%

Estimated Maturities of Long-Term Debt

Estimated maturities of long-term debt for the next five years are (in thousands):

	Southwest		Centuri		Total
2019	$	—	$	33,060	$	33,060
2020	125,000		38,296		163,296
2021	—		33,571		33,571
2022	425,000		35,515		460,515
2023	—		178,614		178,614