REGULATORY ASSETS AND LIABILITIES (Notes)

3 Months Ended

Mar. 31, 2019

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:

	March 31, 2019
	Current			Noncurrent			Total
	(Thousands of dollars)
Pension and postemployment benefit costs	$	22,967		$	414,253		$	437,220
Reacquired debt costs	812			6,285			7,097
MGP remediation costs	98			7,611			7,709
Other	14,883			1,369			16,252
Total regulatory assets, net of amortization	38,760			429,518			468,278
Federal corporate income tax rate changes (a)	(32,312		)	(511,743		)	(544,055		)
Over-recovered purchased-gas costs	(14,197		)	—			(14,197		)
Weather normalization	(8,282		)	—			(8,282		)
Total regulatory liabilities	(54,791		)	(511,743		)	(566,534		)
Net regulatory liabilities	$	(16,031	)	$	(82,225	)	$	(98,256	)

(a)See Note 11 for additional information regarding our federal corporate income tax rate changes to regulatory liabilities.

	December 31, 2018
	Current			Noncurrent			Total
	(Thousands of dollars)
Under-recovered purchased-gas costs	$	25,083		$	—		$	25,083
Pension and postemployment benefit costs	23,384			421,726			445,110
Reacquired debt costs	812			6,487			7,299
MGP remediation costs	—			7,724			7,724
Other (a)	5,141			1,542			6,683
Total regulatory assets, net of amortization	54,420			437,479			491,899
Federal corporate income tax rate changes (b)	(30,934		)	(520,866		)	(551,800		)
Over-recovered purchased-gas costs	(13,668		)	—			(13,668		)
Weather normalization	(3,792		)	—			(3,792		)
Total regulatory liabilities	(48,394		)	(520,866		)	(569,260		)
Net regulatory assets (liabilities)	$	6,026		$	(83,387	)	$	(77,361	)

(a) Includes reclassification of ad-valorem tax for consistency with the current year presentation.

(b)See Note 11 for additional information regarding our federal corporate income tax rate changes to regulatory liabilities.

Regulatory assets in our consolidated balance sheets, as authorized by various regulatory authorities, are probable of recovery. Base rates and certain riders 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.