Selected Balance Sheet Data (Tables)

3 Months Ended

Mar. 31, 2017

Balance Sheet Related Disclosures [Abstract]

Accounts Receivable, Net

(Thousands of Dollars)	March 31, 2017			Dec. 31, 2016
Accounts receivable, net
Accounts receivable	$	832,540		$	827,112
Less allowance for bad debts	(51,292		)	(50,823		)
	$	781,248		$	776,289

Inventories

(Thousands of Dollars)	March 31, 2017		Dec. 31, 2016
Inventories
Materials and supplies	$	321,518	$	312,430
Fuel	150,025		181,752
Natural gas	47,538		110,044
	$	519,081	$	604,226

Property, Plant and Equipment, Net

(Thousands of Dollars)	March 31, 2017			Dec. 31, 2016
Property, plant and equipment, net
Electric plant	$	38,412,137		$	38,220,765
Natural gas plant	5,365,655			5,317,717
Common and other property	1,897,263			1,888,518
Plant to be retired (a)	22,202			31,839
Construction work in progress	1,596,909			1,373,380
Total property, plant and equipment	47,294,166			46,832,219
Less accumulated depreciation	(14,576,320		)	(14,381,603		)
Nuclear fuel	2,652,026			2,571,770
Less accumulated amortization	(2,211,488		)	(2,180,636		)
	$	33,158,384		$	32,841,750

^(a)  In the fourth quarter of 2017, PSCo expects to both early retire Valmont Unit 5 and convert Cherokee Unit 4 from a coal-fueled generating facility to natural gas. PSCo also expects Craig Unit 1 to be early retired in approximately 2025. Amounts are presented net of accumulated depreciation.