Percentage of domestic federal statutory tax rate applicable to pretax income (loss).

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The amount deducted from an entities' taxes, reflecting a percentage of an amount invested in certain assets spread over the useful life of those assets; includes deferred investment tax credits.

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Amount of operating loss carryforward, before tax effects, available to reduce future taxable income under enacted tax laws.

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Amount of increase (decrease) to previously recorded tax expense. Includes, but is not limited to, significant settlements of income tax disputes, and unusual tax positions or infrequent actions taken by the entity, including tax assessment reversal, and IRS tax settlement.

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Amount of income tax expense (benefit) from effect of Tax Cuts and Jobs Act.

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Amount of interest expense accrued for an underpayment of income taxes.

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Income Taxes [Line Items]

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Number Of Federal Renewable Energy Tax Credit Funds

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Number Of Solar Generator Units

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Number Of Tax Opinions

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Percentage Of Solar Generator Units Positively Identified

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Percentage Of The Tax Credit Recognized And Measured For Each Tax Position

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Income Taxes - Additional Information (Detail)	3 Months Ended	12 Months Ended			36 Months Ended
Income Taxes - Additional Information (Detail)	Mar. 31, 2019 fund	Dec. 31, 2019 USD ($) fund solar_generator_unit	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2015 USD ($) tax_opinion
Income Taxes [Line Items]
Tax benefit related to effects of TCJA			$ 2,300,000
Statutory federal income tax rate		21.00%	21.00%	35.00%
Number of federal renewable energy tax credit funds \| fund	3	3
Number of solar generator units \| solar_generator_unit		512
Federal tax credit benefit					$ 22,800,000
Number of tax opinions \| tax_opinion					2
Tax credit recognized and measured for each tax position (as a percent)		100.00%
Percentage of solar generator units positively identified (over)		97.00%
Increase to the provision for income taxes		$ 31,100,000
Uncertain tax position, accrued interest		6,100,000	$ 0	$ 1,800,000
Federal
Income Taxes [Line Items]
Operating loss carryforwards		72,100,000
Obligations of states and state agencies
Income Taxes [Line Items]
Operating loss carryforwards		85,300,000
Capital loss carryforward
Income Taxes [Line Items]
Capital loss carryforwards		$ 3,100,000