Debt (Tables)

12 Months Ended

Dec. 31, 2021

Debt Disclosure [Abstract]

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

Carrying amounts of long-term debt and related estimated fair values as of December 31, 2021 and 2020 are disclosed in the following table. The fair value hierarchy is described in Note 1 - Background, Organization, and Summary of Significant Accounting Policies.

	December 31,
	2021				2020
	Carrying Amount		Fair Value		Carrying Amount		Fair Value
(Thousands of dollars)
Southwest Gas Corporation:
Debentures:
Notes, 6.1%, due 2041	$	125,000	$	166,380	$	125,000	$	174,858
Notes, 3.875%, due 2022	250,000		250,603		250,000		258,825
Notes, 4.875%, due 2043	250,000		307,538		250,000		317,190
Notes, 3.8%, due 2046	300,000		329,055		300,000		347,046
Notes, 3.7%, due 2028	300,000		325,191		300,000		344,553
Notes, 4.15%, due 2049	300,000		342,030		300,000		370,278
Notes, 2.2%, due 2030	450,000		440,838		450,000		474,552
Notes 3.18%, due 2051	300,000		292,116		—		—
8% Series, due 2026	75,000		92,623		75,000		99,723
Medium-term notes, 7.78% series, due 2022	25,000		25,122		25,000		26,663
Medium-term notes, 7.92% series, due 2027	25,000		31,555		25,000		33,802
Medium-term notes, 6.76% series, due 2027	7,500		8,949		7,500		9,613
Unamortized discount and debt issuance costs	(19,959)				(17,822)
	2,387,541				2,089,678
Revolving credit facility and commercial paper	130,000		130,000		150,000		150,000
Industrial development revenue 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	(1,938)				(1,472)
	198,062				198,528
Less: current maturities	(275,000)				—
Southwest Gas Corporation total long-term debt, less current maturities	$	2,440,603			$	2,438,206
Southwest Gas Holdings, Inc.:
Centuri secured term loan facility	$	1,117,138	$	1,117,841	$	226,648	$	230,824
Centuri secured revolving credit facility	103,329		103,749		26,626		26,645
MountainWest unsecured senior notes, 3.53%, due in 2028	102,078		102,078		—		—
MountainWest unsecured senior notes, 4.875%, due in 2041	199,926		199,926		—		—
MountainWest unsecured senior notes, 3.91%, due in 2038	147,735		147,735		—		—
Other debt obligations	51,665		50,003		81,973		84,246
Unamortized discount and debt issuance costs	(24,466)				(820)
Less: current maturities	(22,324)				(40,433)
Southwest Gas Holdings, Inc. total long-term debt, less current maturities	$	4,115,684			$	2,732,200

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,
	2021		2020
2003 Series A	0.91	%	0.80	%
2008 Series A	0.90	%	0.83	%
2009 Series A	0.88	%	0.76	%
Tax-exempt Series A	0.92	%	0.87	%

Estimated Maturities of Long-Term Debt

Estimated maturities of long-term debt for the next five years are:

(Thousands of dollars)	2022		2023		2024		2025		2026		Total
Southwest Gas Corporation:
Debentures	$	275,000	$	—	$	—	$	—	$	75,000	$	350,000
Revolving credit facility and commercial paper	—		—		—		130,000		—		130,000
Total	275,000		—		—		130,000		75,000		480,000
Southwest Gas Holdings, Inc.:
Centuri secured term loan facility	11,450		11,450		11,450		11,450		11,450		57,250
Centuri secured revolving credit facility	—		—		—		—		103,329		103,329
Other debt obligations	10,874		11,047		11,285		9,076		7,490		49,772
Total	$	297,324	$	22,497	$	22,735	$	150,526	$	197,269	$	690,351