Regulatory Assets and Liabilities (Tables)

12 Months Ended

Dec. 31, 2016

Regulatory Assets and Liabilities Disclosure [Abstract]

Regulatory Assets

The components of regulatory assets shown on the consolidated balance sheets of NSP-Wisconsin at Dec. 31, 2016 and 2015 are:

(Thousands of Dollars)	See Note(s)	Remaining Amortization Period	Dec. 31, 2016				Dec. 31, 2015
Regulatory Assets			Current		Noncurrent		Current		Noncurrent
Environmental remediation costs	1, 11	Various	$	10,669	$	148,880	$	6,702	$	160,699
Pension and retiree medical obligations (a)	7	Various	5,989		93,160		6,415		86,778
Recoverable deferred taxes on AFUDC recorded in plant	1	Plant lives	—		22,345		—		20,586
State commission adjustments	1	Plant lives	703		14,008		724		12,945
Losses on reacquired debt	4	Term of related debt	801		3,333		803		4,134
Deferred income tax adjustment	1, 6	Typically plant lives	—		2,078		—		2,250
Other		Various	—		2,384		1,502		1,804
Total regulatory assets			$	18,162	$	286,188	$	16,146	$	289,196

^(a)  Includes the non-qualified pension plan.

Regulatory Liabilities

The components of regulatory liabilities shown on the consolidated balance sheets of NSP-Wisconsin at Dec. 31, 2016 and 2015 are:

(Thousands of Dollars)	See Note(s)	Remaining Amortization Period	Dec. 31, 2016				Dec. 31, 2015
Regulatory Liabilities			Current		Noncurrent		Current		Noncurrent
Plant removal costs	11	Plant lives	$	—	$	139,735	$	—	$	132,311
Investment tax credit deferrals	1, 6	Various	—		8,342		—		8,869
Deferred electric production and natural gas costs	1	Less than one year	11,377		—		9,386		—
DOE settlement	11	Less than one year	4,822		—		1,996		—
Conservation programs	1	Less than one year	1,122		—		339		—
Other		Various	107		112		60		109
Total regulatory liabilities			$	17,428	$	148,189	$	11,781	$	141,289