Regulatory Assets and Liabilities (Tables)

12 Months Ended

Dec. 31, 2020

Regulatory Assets and Liabilities Disclosure [Abstract]

Regulatory Assets

Components of regulatory assets:

(Millions of Dollars)	See Note(s)	Remaining Amortization Period	Dec. 31, 2020				Dec. 31, 2019
Regulatory Assets			Current		Noncurrent		Current		Noncurrent
Environmental remediation costs	1, 10	Various	$	13	$	94	$	35	$	108
Pension and retiree medical obligations	9	Various	4		67		12		70
State commission adjustments		Plant lives	1		20		1		19
Recoverable deferred taxes on AFUDC		Plant lives	—		18		—		17
Losses on reacquired debt		Term of related debt	—		2		—		2
Excess deferred taxes — TCJA	7	Various	—		—		23		—
Other		Various	1		14		1		8
Total regulatory assets			$	19	$	215	$	72	$	224

Regulatory Liabilities

Components of regulatory liabilities:

(Millions of Dollars)	See Note(s)	Remaining Amortization Period	Dec. 31, 2020				Dec. 31, 2019
Regulatory Liabilities			Current		Noncurrent		Current		Noncurrent
Plant removal costs	1, 10	Various	$	—	$	184	$	—	$	171
Deferred income tax adjustments and TCJA refunds (a)	7	Various	—		161		51		196
Deferred electric production and natural gas costs		Less than one year	17		1		17		—
United States Department of Energy Settlement		Less than one year	12		—		10		—
Other		Various	2		4		1		4
Total regulatory liabilities			$	31	$	350	$	79	$	371

(a)    Includes the revaluation of recoverable/regulated plant ADIT and revaluation impact of non-plant ADIT due to the TCJA.

^[1]

[1] Includes the revaluation of recoverable/regulated plant ADIT and revaluation impact of non-plant ADIT due to the TCJA.