Details of the regulatory assets and liabilities are presented in the following table:

Regulatory Assets and Liabilities
(millions)	March 31, 2017		December 31, 2016
Regulatory assets:
Regulatory tax asset ⁽¹⁾	$	85	$	86
Cost-recovery clauses - deferred balances ⁽²⁾		10		8
Environmental remediation⁽³⁾		35		37
Postretirement benefits ⁽⁴⁾		269		272
Other		20		18
Total regulatory assets		419		421
Less: Current portion		29		28
Long-term regulatory assets	$	390	$	393
Regulatory liabilities:
Regulatory tax liability	$	12	$	6
Cost-recovery clauses - deferred balances ⁽²⁾		91		112
Cost-recovery clauses - offsets to derivative assets⁽²⁾		6		17
Transmission and delivery storm reserve		47		56
Accumulated reserve - cost of removal⁽⁵⁾		545		547
Other		7		7
Total regulatory liabilities		708		745
Less: Current portion		124		154
Long-term regulatory liabilities	$	584	$	591

(1)

The regulatory tax asset is primarily associated with the depreciation and recovery of AFUDC-equity. This asset does not earn a return but rather is included in the capital structure, which is used in the calculation of the weighted cost of capital used to determine revenue requirements. It will be recovered over the expected life of the related assets.

(2)

These assets and liabilities are related to FPSC clauses and riders. They are recovered or refunded through cost-recovery mechanisms approved by the FPSC on a dollar-for-dollar basis in the next year. In the case of the regulatory liability related to derivative assets, refund occurs in the year following the settlement of the derivative position.

(3)

This asset is related to costs associated with environmental remediation primarily at MGP sites. The balance is included in rate base, partially offsetting the related liability, and earns a rate of return as permitted by the FPSC. The timing of recovery is based on a settlement agreement approved by the FPSC.

(4)

This asset is related to the deferred costs of postretirement benefits and it is amortized over the remaining service life of plan participants. Deferred costs of postretirement benefits that are included in expense are recognized as cost of service for rate-making purposes as permitted by the FPSC.

(5)

This item represents the non-ARO cost of removal in the accumulated reserve for depreciation. AROs are costs for legally required removal of property, plant and equipment. Non-ARO cost of removal represent estimated funds received from customers through depreciation rates to cover future non-legally required cost of removal of property, plant and equipment, net of salvage value upon retirement, which reduces rate base for ratemaking purposes. This liability is reduced as costs of removal are incurred.