Income Taxes	3 Months Ended
Mar. 31, 2018
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes For periods through December 31, 2017, when NEP acquired a NEER project, income taxes were calculated on the predecessor method using the separate return method applied to the group of renewable energy projects acquired. As a result of the governance changes discussed in Note 1, beginning in January 2018, acquisitions from NEER are no longer treated as common control acquisitions, and income taxes are calculated on the successor method where taxes are calculated for NEP as a single taxpaying corporation for U.S. federal and state income taxes (based on its election to be taxed as a corporation). Because NEP OpCo is a limited partnership, NEP only recognizes in income its applicable ownership share of U.S. income taxes related to the U.S. and Canadian projects, allocated by NEP OpCo. NEP's Canadian subsidiaries are all Canadian taxpayers, and therefore NEP recognizes in income all of the Canadian taxes. Income taxes include NEP's applicable ownership share of U.S. taxes and 100% of Canadian taxes. Net income or loss attributable to noncontrolling interests includes no U.S. taxes and NEER's applicable ownership share of Canadian taxes. Net income attributable to NEP includes NEP's applicable ownership share of U.S. and Canadian taxes. On December 22, 2017, the Tax Cuts and Jobs Act (tax reform) was signed into law which, among other things, reduced the federal corporate income tax rate from 35% to 21% effective January 1, 2018. As a result, NEP performed an analysis to preliminarily revalue its deferred income taxes and included an estimate of changes in the balances in NEP's December 31, 2017 financial statements. At December 31, 2017, the revaluation reduced NEP’s net deferred income tax assets by approximately $101 million, which decreased NEP’s 2017 net income and net income attributable to NEP. While NEP continues to believe that the provisional tax reform adjustment is a reasonable estimate of the effects on its existing deferred taxes, additional analysis and detailed reviews are still being performed to finalize the accounting for the remeasurement of deferred tax assets and liabilities as a result of the enactment of tax reform. The effective tax rates for the three months ended March 31, 2018 and 2017 were approximately (950)% and 19%, respectively. The effective tax rate is affected by recurring items, such as the relative amount of income earned in jurisdictions (earnings mix), valuation allowances on deferred tax assets, taxes attributable to the noncontrolling interests and the taxation of Canadian income in both Canada and the U.S. During the three months ended March 31, 2018, NEP recorded an income tax charge of approximately $20 million related to the $231 million adjustment to differential membership interests as a result of the change in federal corporate income taxes due to tax reform that became effective January 1, 2018 (see Note 10 - Accounting for Partial Sales of Nonfinancial Assets).

Income Taxes

For periods through December 31, 2017, when NEP acquired a NEER project, income taxes were calculated on the predecessor method using the separate return method applied to the group of renewable energy projects acquired. As a result of the governance changes discussed in Note 1, beginning in January 2018, acquisitions from NEER are no longer treated as common control acquisitions, and income taxes are calculated on the successor method where taxes are calculated for NEP as a single taxpaying corporation for U.S. federal and state income taxes (based on its election to be taxed as a corporation). Because NEP OpCo is a limited partnership, NEP only recognizes in income its applicable ownership share of U.S. income taxes related to the U.S. and Canadian projects, allocated by NEP OpCo. NEP's Canadian subsidiaries are all Canadian taxpayers, and therefore NEP recognizes in income all of the Canadian taxes. Income taxes include NEP's applicable ownership share of U.S. taxes and 100% of Canadian taxes. Net income or loss attributable to noncontrolling interests includes no U.S. taxes and NEER's applicable ownership share of Canadian taxes. Net income attributable to NEP includes NEP's applicable ownership share of U.S. and Canadian taxes.

On December 22, 2017, the Tax Cuts and Jobs Act (tax reform) was signed into law which, among other things, reduced the federal corporate income tax rate from 35% to 21% effective January 1, 2018. As a result, NEP performed an analysis to preliminarily revalue its deferred income taxes and included an estimate of changes in the balances in NEP's December 31, 2017 financial statements. At December 31, 2017, the revaluation reduced NEP’s net deferred income tax assets by approximately $101 million, which decreased NEP’s 2017 net income and net income attributable to NEP. While NEP continues to believe that the provisional tax reform adjustment is a reasonable estimate of the effects on its existing deferred taxes, additional analysis and detailed reviews are still being performed to finalize the accounting for the remeasurement of deferred tax assets and liabilities as a result of the enactment of tax reform.

The effective tax rates for the three months ended March 31, 2018 and 2017 were approximately (950)% and 19%, respectively. The effective tax rate is affected by recurring items, such as the relative amount of income earned in jurisdictions (earnings mix), valuation allowances on deferred tax assets, taxes attributable to the noncontrolling interests and the taxation of Canadian income in both Canada and the U.S. During the three months ended March 31, 2018, NEP recorded an income tax charge of approximately $20 million related to the $231 million adjustment to differential membership interests as a result of the change in federal corporate income taxes due to tax reform that became effective January 1, 2018 (see Note 10 - Accounting for Partial Sales of Nonfinancial Assets).