Balance Sheet Components (Tables)

The activity in the allowance for uncollectible accounts is as follows (in millions):



	Six Months Ended June 30,
	2015			2014
Balance as of beginning of period	$	6		$	6
Provision, net	3			4
Amounts written off, less recoveries	(3		)	(3		)
Balance as of end of period	$	6		$	7

Other current assets consist of the following (in millions):



	June 30, 2015		December 31, 2014
Prepaid expenses	$	32	$	39
Current deferred income tax asset	33		33
Margin deposits	28		11
Accrued sales tax refund related to Tucannon River Wind Farm	—		23
Assets from price risk management activities	3		6
Other	1		3
Other current assets	$	97	$	115

Electric utility plant, net consists of the following (in millions):



	June 30, 2015			December 31, 2014
Electric utility plant	$	8,301		$	8,161
Construction work-in-progress	557			417
Total cost	8,858			8,578
Less: accumulated depreciation and amortization	(2,984		)	(2,899		)
Electric utility plant, net	$	5,874		$	5,679

Regulatory assets and liabilities consist of the following (in millions):



	June 30, 2015					December 31, 2014
	Current			Noncurrent		Current			Noncurrent
Regulatory assets:
Price risk management	$	98		$	186	$	100		$	121
Pension and other postretirement plans	—			237		—			247
Deferred income taxes	—			87		—			86
Debt issuance costs	—			17		—			15
Deferred capital projects	10			—		19			—
Other	9			25		14			25
Total regulatory assets	$	117		$	552	$	133		$	494
Regulatory liabilities:
Asset retirement removal costs	$	—		$	824	$	—		$	804
Trojan decommissioning activities	21			24		23			34
Asset retirement obligations	—			42		—			39
Other	32			33		37			29
Total regulatory liabilities	$	53	^*	$	923	$	60	^*	$	906


*	Included in Accrued expenses and other current liabilities in the condensed consolidated balance sheets.

Accrued expenses and other current liabilities consist of the following (in millions):



	June 30, 2015		December 31, 2014
Regulatory liabilities—current	$	53	$	60
Accrued employee compensation and benefits	43		51
Accrued interest payable	25		26
Accrued dividends payable	27		23
Accrued taxes payable	21		22
Other	59		54
Total accrued expenses and other current liabilities	$	228	$	236

Asset retirement obligations (AROs) consist of the following (in millions):



	June 30, 2015		December 31, 2014
Trojan decommissioning activities	$	43	$	41
Utility plant	81		64
Non-utility property	11		11
Asset retirement obligations	$	135	$	116

Components of net periodic benefit cost are as follows (in millions):



	Defined Benefit Pension Plan						Other Postretirement Benefits						Non-Qualified Benefit Plans
	2015			2014			2015			2014			2015		2014
Three Months Ended June 30:
Service cost	$	5		$	3		$	1		$	1		$	—	$	—
Interest cost	8			8			1			1			1		1
Expected return on plan assets	(10		)	(10		)	(1		)	(1		)	—		—
Amortization of prior service cost	—			—			—			1			—		—
Amortization of net actuarial loss	5			5			—			—			—		—
Net periodic benefit cost	$	8		$	6		$	1		$	2		$	1	$	1
Six Months Ended June 30:
Service cost	$	9		$	7		$	2		$	1		$	—	$	—
Interest cost	16			17			2			2			1		1
Expected return on plan assets	(20		)	(20		)	(1		)	(1		)	—		—
Amortization of prior service cost	—			—			—			1			—		—
Amortization of net actuarial loss	10			9			—			—			—		—
Net periodic benefit cost	$	15		$	13		$	3		$	3		$	1	$	1