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Regulatory Matters (Details) - USD ($) $ in Thousands | Mar. 31, 2021 | Dec. 31, 2020
--- | --- | ---
Regulatory assets |  |
Regulatory assets | $ 802,257 | $ 278,258
Less current regulatory assets | (129,951) | (51,676)
Regulatory assets, non-current | 672,306 | 226,582
Regulatory liabilities |  |
Regulatory liabilities | 511,390 | 532,720
Less current regulatory liabilities | (13,580) | (25,061)
Regulatory liabilities, non-current | 497,810 | 507,659
Deferred energy and gas costs |  |
Regulatory liabilities |  |
Regulatory liabilities | 426 | 13,253
Employee benefit plans |  |
Regulatory liabilities |  |
Regulatory liabilities | 40,471 | 40,256
Cost of removal |  |
Regulatory liabilities |  |
Regulatory liabilities | 177,003 | 172,902
Excess deferred income taxes |  |
Regulatory liabilities |  |
Regulatory liabilities | 271,492 | 285,259
Other regulatory liabilities |  |
Regulatory liabilities |  |
Regulatory liabilities | 21,998 | 21,050
Deferred energy and gas costs |  |
Regulatory assets |  |
Regulatory assets | 68,402 | 39,035
Deferred gas cost adjustments |  |
Regulatory assets |  |
Regulatory assets | 17,066 | 3,200
Gas price derivatives |  |
Regulatory assets |  |
Regulatory assets | 324 | 2,226
Deferred taxes on AFUDC |  |
Regulatory assets |  |
Regulatory assets | 7,469 | 7,491
Employee benefit plans |  |
Regulatory assets |  |
Regulatory assets | 117,886 | 116,598
Environmental |  |
Regulatory assets |  |
Regulatory assets | 1,413 | 1,413
Loss on reacquired debt |  |
Regulatory assets |  |
Regulatory assets | 22,386 | 22,864
Deferred taxes on flow through accounting |  |
Regulatory assets |  |
Regulatory assets | 51,823 | 47,515
Decommissioning costs |  |
Regulatory assets |  |
Regulatory assets | 7,827 | 8,988
Gas supply contract termination |  |
Regulatory assets |  |
Regulatory assets | 1,013 | 2,524
Other regulatory assets |  |
Regulatory assets |  |
Regulatory assets | 25,806 | 26,404
Winter Storm Uri Incremental Costs in a Separately Tracked Mechanism |  |
Regulatory assets |  |
Regulatory assets | $ 480,842 | $ 0

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- Definition Carrying amount as of the balance sheet date of capitalized costs of regulated entities that are expected to be recovered through revenue sources within one year or the normal operating cycle, if longer. Such costs are capitalized if they meet both of the following criteria: a. It is probable that future revenue in an amount at least equal to the capitalized cost will result from inclusion of that cost in allowable costs for rate-making purposes. b. Based on available evidence, the future revenue will be provided to permit recovery of the previously incurred cost rather than to provide for expected levels of similar future costs. If the revenue will be provided through an automatic rate-adjustment clause, this criterion requires that the regulator's intent clearly be to permit recovery of the previously incurred cost. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 980 -SubTopic 340 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6499975&loc=d3e44250-110382 + Details
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