Regulatory Assets and Liabilities (Tables)

12 Months Ended

Dec. 31, 2015

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, 2015 and 2014 are:

(Thousands of Dollars)	See Note(s)	Remaining Amortization Period	Dec. 31, 2015				Dec. 31, 2014
Regulatory Assets			Current		Noncurrent		Current		Noncurrent
Environmental remediation costs	1, 11	Various	$	6,702	$	160,699	$	4,376	$	147,793
Pension and retiree medical obligations (a)	7	Various	6,415		86,778		6,837		91,601
Recoverable deferred taxes on AFUDC recorded in plant	1	Plant lives	—		20,586		—		16,711
State commission adjustments	1	Plant lives	724		12,945		488		11,650
Losses on reacquired debt	4	Term of related debt	803		4,134		801		4,936
Deferred income tax adjustment	1, 6	Typically plant lives	—		2,250		—		1,514
Recoverable purchased natural gas and electric energy costs		Less than one year	1,032		—		6,946		—
Monticello EPU		N/A	—		—		—		5,237
Other		Various	470		1,804		588		1,251
Total regulatory assets			$	16,146	$	289,196	$	20,036	$	280,693

^(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, 2015 and 2014 are:

(Thousands of Dollars)	See Note(s)	Remaining Amortization Period	Dec. 31, 2015				Dec. 31, 2014
Regulatory Liabilities			Current		Noncurrent		Current		Noncurrent
Plant removal costs	11	Plant lives	$	—	$	132,311	$	—	$	123,105
Investment tax credit deferrals	1, 6	Various	—		8,869		—		9,397
Deferred electric production and natural gas costs	1	Less than one year	9,386		—		—		—
DOE settlement	11	One to two years	1,996		—		4,931		—
Conservation programs	1	Less than one year	339		—		1,010		—
Excess depreciation reserve		Less than one year	60		—		10,999		—
Other		Various	—		109		—		172
Total regulatory liabilities			$	11,781	$	141,289	$	16,940	$	132,674