Selected Balance Sheet Data (Tables)

3 Months Ended

Mar. 31, 2016

Balance Sheet Related Disclosures [Abstract]

Accounts Receivable, Net

(Thousands of Dollars)	March 31, 2016			Dec. 31, 2015
Accounts receivable, net
Accounts receivable	$	778,953		$	776,494
Less allowance for bad debts	(49,567		)	(51,888		)
	$	729,386		$	724,606

Inventories

(Thousands of Dollars)	March 31, 2016		Dec. 31, 2015
Inventories
Materials and supplies	$	298,345	$	290,690
Fuel	172,098		202,271
Natural gas	49,611		115,623
	$	520,054	$	608,584

Property, Plant and Equipment, Net

(Thousands of Dollars)	March 31, 2016			Dec. 31, 2015
Property, plant and equipment, net
Electric plant	$	36,604,585		$	36,464,050
Natural gas plant	5,017,324			4,944,757
Common and other property	1,720,351			1,709,508
Plant to be retired (a)	34,606			38,249
Construction work in progress	1,486,070			1,256,949
Total property, plant and equipment	44,862,936			44,413,513
Less accumulated depreciation	(13,790,489		)	(13,591,259		)
Nuclear fuel	2,450,363			2,447,251
Less accumulated amortization	(2,089,404		)	(2,063,654		)
	$	31,433,406		$	31,205,851

^(a)  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.