REGULATORY ASSETS AND LIABILITIES (Notes)

9 Months Ended

Sep. 30, 2018

SCHEDULE OF REGULATED ASSETS AND LIABILITIES [Line Items]

Schedule of Regulatory Assets and Liabilities

3. REGULATORY ASSETS AND LIABILITIES

The tables below present a summary of regulatory assets, net of amortization, and liabilities for the periods indicated:

	September 30, 2018
	Current			Noncurrent			Total
	(Thousands of dollars)
Under-recovered purchased-gas costs	$	16,727		$	—		$	16,727
Pension and postemployment benefit costs	25,109			357,723			382,832
Reacquired debt costs	812			6,690			7,502
MGP remediation costs	—			7,724			7,724
Ad valorem tax	1,029			—			1,029
Other	5,362			2,922			8,284
Total regulatory assets, net of amortization	49,039			375,059			424,098
Federal income tax rate changes (a)	(19,447		)	(521,717		)	(541,164		)
Over-recovered purchased-gas costs	(22,218		)	—			(22,218		)
Total regulatory liabilities	(41,665		)	(521,717		)	(563,382		)
Net regulatory assets (liabilities)	$	7,374		$	(146,658	)	$	(139,284	)

(a)See Note 10 for additional information regarding our federal income tax rate changes to regulatory liabilities.

	December 31, 2017
	Current			Noncurrent			Total
	(Thousands of dollars)
Under-recovered purchased-gas costs	$	41,238		$	—		$	41,238
Pension and postemployment benefit costs	25,156			387,582			412,738
Weather normalization	17,461			—			17,461
Reacquired debt costs	812			7,298			8,110
MGP remediation costs	—			6,104			6,104
Other	3,513			4,205			7,718
Total regulatory assets, net of amortization	88,180			405,189			493,369
Federal income tax rate changes (a)	—			(519,421		)	(519,421		)
Over-recovered purchased-gas costs	(9,434		)	—			(9,434		)
Ad valorem tax	(4		)	—			(4		)
Total regulatory liabilities	(9,438		)	(519,421		)	(528,859		)
Net regulatory assets (liabilities)	$	78,742		$	(114,232	)	$	(35,490	)

(a)See Note 10 for additional information regarding our federal income tax rate changes to regulatory liabilities.

Regulatory assets on our Consolidated Balance Sheets, as authorized by various regulatory authorities, are probable of recovery. Base rates are designed to provide a recovery of costs during the period such rates are in effect, but do not generally provide for a return on investment for amounts we have deferred as regulatory assets. All of our regulatory assets are subject to review by the respective regulatory authorities during future regulatory proceedings. We are not aware of any evidence that these costs will not be recoverable through either riders or base rates, and we believe that we will be able to recover such costs, consistent with our historical recoveries.