Long-Term Debt (Tables)

9 Months Ended

Sep. 30, 2016

Debt Disclosure [Abstract]

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

Since 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.

	September 30, 2016					December 31, 2015
	Carrying			Market		Carrying			Market
	Amount			Value		Amount			Value
(Thousands of dollars)
Debentures:
Notes, 4.45%, due 2020	$	125,000		$	133,819	$	125,000		$	130,273
Notes, 6.1%, due 2041		125,000			162,340		125,000			141,581
Notes, 3.875%, due 2022		250,000			260,813		250,000			253,600
Notes, 4.875%, due 2043		250,000			295,000		250,000			251,483
Notes, 3.8%, due 2046		300,000			303,789		—			—
8% Series, due 2026		75,000			101,275		75,000			97,035
Medium-term notes, 7.59% series, due 2017		25,000			25,350		25,000			26,253
Medium-term notes, 7.78% series, due 2022		25,000			30,610		25,000			29,855
Medium-term notes, 7.92% series, due 2027		25,000			34,190		25,000			31,890
Medium-term notes, 6.76% series, due 2027		7,500			9,404		7,500			8,684
Unamortized discount and debt issuance costs		(9,901	)				(6,137	)
		1,197,599					901,363
Revolving credit facility and commercial paper		—			—		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
Fixed-rate bonds:
4.85% 2005 Series A, due 2035		—			—		100,000			100,452
4.75% 2006 Series A, due 2036		—			—		24,855			25,130
Unamortized discount and debt issuance costs		(2,591	)				(3,946	)
		197,409					320,909
Centuri term loan facility		111,612			111,767		112,571			112,665
Unamortized debt issuance costs		(560	)				(692	)
		111,052					111,879
Centuri secured revolving credit facility		79,932			80,479		60,627			60,724
Centuri other debt obligations		56,434			58,553		25,901			26,059
		1,642,426					1,570,679
Less: current maturities		(49,480	)				(19,475	)
Long-term debt, less current maturities	$	1,592,946				$	1,551,204