Long-Term Debt (Tables)

3 Months Ended

Mar. 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 (not actively traded) 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.

	March 31, 2018					December 31, 2017
	Carrying			Fair		Carrying			Fair
	Amount			Value		Amount			Value
(Thousands of dollars)
Southwest Gas Corporation:
Debentures:
Notes, 4.45%, due 2020	$	125,000		$	127,630	$	125,000		$	129,273
Notes, 6.1%, due 2041		125,000			155,349		125,000			158,304
Notes, 3.875%, due 2022		250,000			252,270		250,000			256,163
Notes, 4.875%, due 2043		250,000			284,998		250,000			283,243
Notes, 3.8%, due 2046		300,000			291,945		300,000			302,970
Notes, 3.7%, due 2028		300,000			302,520		—			—
8% Series, due 2026		75,000			95,542		75,000			96,063
Medium-term notes, 7.78% series, due 2022		25,000			28,147		25,000			28,714
Medium-term notes, 7.92% series, due 2027		25,000			30,810		25,000			31,542
Medium-term notes, 6.76% series, due 2027		7,500			8,811		7,500			8,882
Unamortized discount and debt issuance costs		(12,480	)				(9,350	)
		1,470,020					1,173,150
Revolving credit facility and commercial paper		39,000			39,000		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		(2,026	)				(2,119	)
		197,974					197,881
Less: current maturities		—					—
Long-term debt, less current maturities - Southwest Gas Corporation	$	1,706,994				$	1,521,031
Centuri:
Centuri term loan facility	$	194,357			195,757	$	199,578			207,588
Unamortized debt issuance costs		(1,056	)				(1,111	)
		193,301					198,467
Centuri secured revolving credit facility		79,227			79,261		56,472			56,525
Centuri other debt obligations		43,472			43,256		47,952			48,183
Less: current maturities		(24,867	)				(25,346	)
Long-term debt, less current maturities - Centuri	$	291,133				$	277,545
Consolidated Southwest Gas Holdings, Inc.:
Southwest Gas Corporation long-term debt	$	1,706,994				$	1,521,031
Centuri long-term debt		316,000					302,891
Less: current maturities		(24,867	)				(25,346	)
Long-term debt, less current maturities - Southwest Gas Holdings, Inc.	$	1,998,127				$	1,798,576