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Income Taxes - Reconciliation of Provision for Income Taxes with Federal Statutory Income Tax Rate (Detail) - USD ($) $ in Millions | 12 Months Ended
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Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Income Tax Disclosure [Abstract] |  |  |
Federal statutory rate | $ 182.9 | $ 131.5 | $ 100.7
State income taxes - net of Federal benefit | 22.2 | 4.4 | 8.5
Differences related to non U.S. operations | (2.5) | (10.1) | (14.8)
Alternative energy and other tax credits | (154.3) | (196.1) | (252.9)
Other permanent differences | (15.7) | (7.6) | 0.9
U.S. repatriation tax |  |  | (1.8)
Stock-based compensation | (31.4) | (16.2) | (15.0)
Changes in unrecognized tax benefits |  | 0.8 | (0.2)
Change in valuation allowance | 6.5 | 7.5 | (22.0)
Change in U.S. and U.K. tax rates | 5.5 | (3.7) |
Other | (0.4) | (0.2) | 0.1
Total provision (benefit) for income taxes | $ 12.8 | $ (89.7) | $ (196.5)
Federal statutory rate, % of Pretax Earnings | 21.00% | 21.00% | 21.00%
State income taxes-net of Federal benefit, % of Pretax Earnings | 2.60% | 0.70% | 1.80%
Differences related to non U.S. operations, % of Pretax Earnings | (0.30%) | (1.60%) | (3.10%)
Alternative energy and other tax credits, % of Pretax Earnings | (17.70%) | (31.30%) | (52.80%)
Other permanent differences, % of Pretax Earnings | (1.80%) | (1.20%) | 0.20%
U.S. repatriation tax |  |  | (0.40%)
Stock-based compensation | (3.60%) | (2.60%) | (3.10%)
Changes in unrecognized tax benefits, % of Pretax Earnings |  | 0.10% |
Change in valuation allowance, % of Pretax Earnings | 0.70% | 1.20% | (4.60%)
Change in U.S. and U.K. tax rates | 0.60% | (0.60%) |
Total provision (benefit) for income taxes, % of Pretax Earnings | 1.50% | (14.30%) | (41.00%)

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- Definition The increase (decrease) during the reporting period in differences between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to repatriation of foreign earnings. + References No definition available. + Details
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