Selected Balance Sheet Data (Tables)

12 Months Ended

Dec. 31, 2016

Balance Sheet Related Disclosures [Abstract]

Accounts Receivable, Net

(Thousands of Dollars)	Dec. 31, 2016			Dec. 31, 2015
Accounts receivable, net
Accounts receivable	$	324,512		$	321,004
Less allowance for bad debts	(19,612		)	(20,122		)
	$	304,900		$	300,882

Inventories

(Thousands of Dollars)	Dec. 31, 2016		Dec. 31, 2015
Inventories
Materials and supplies	$	66,161	$	58,128
Fuel	66,429		78,586
Natural gas	69,630		68,848
	$	202,220	$	205,562

Property, Plant and Equipment, Net

(Thousands of Dollars)	Dec. 31, 2016			Dec. 31, 2015
Property, plant and equipment, net
Electric plant	$	12,304,436		$	11,856,126
Natural gas plant	3,710,772			3,420,249
Common and other property	919,955			862,840
Plant to be retired (a)	31,839			38,249
Construction work in progress	484,340			408,963
Total property, plant and equipment	17,451,342			16,586,427
Less accumulated depreciation	(4,601,543		)	(4,414,216		)
	$	12,849,799		$	12,172,211

^(a)  In 2017, PSCo expects to 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 by approximately 2025.  Amounts are presented net of accumulated depreciation.