Selected Balance Sheet Data (Tables)

12 Months Ended

Dec. 31, 2015

Balance Sheet Related Disclosures [Abstract]

Accounts Receivable, Net

(Thousands of Dollars)	Dec. 31, 2015			Dec. 31, 2014
Accounts receivable, net
Accounts receivable	$	321,004		$	346,007
Less allowance for bad debts	(20,122		)	(23,122		)
	$	300,882		$	322,885

Inventories

(Thousands of Dollars)	Dec. 31, 2015		Dec. 31, 2014
Inventories
Materials and supplies	$	58,128	$	55,491
Fuel	78,586		80,963
Natural gas	68,848		102,525
	$	205,562	$	238,979

Property, Plant and Equipment, Net

(Thousands of Dollars)	Dec. 31, 2015			Dec. 31, 2014
Property, plant and equipment, net
Electric plant	$	11,856,126		$	10,927,867
Natural gas plant	3,420,249			3,210,242
Common and other property	862,840			827,708
Plant to be retired (a)	38,249			71,534
Construction work in progress	408,963			828,620
Total property, plant and equipment	16,586,427			15,865,971
Less accumulated depreciation	(4,414,216		)	(4,239,015		)
	$	12,172,211		$	11,626,956

^(a)  PSCo’s Cherokee Unit 3 was retired in August 2015.  In 2017, PSCo expects to both early retire Valmont Unit 5 and convert Cherokee Unit 4 from a coal-fueled generating facility to natural gas, as approved by the Colorado Public Utilities Commission (CPUC).  Amounts are presented net of accumulated depreciation.