Income Taxes - Reconciliation of Federal Income Tax Statutory Rate and Effective Tax Rate (Detail)	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Federal income tax statutory rate	21.00%	35.00%	35.00%
Federal valuation allowance	0.00%	0.00%	0.00%
Income not subject to federal income tax	(21.50%)	(35.00%)	(35.00%)
State taxes	3.10%	2.90%	6.00%
Effective tax rate on income from continuing operations	2.60%	2.90%	6.00%

Percentage of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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

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Percentage of the difference 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 changes in the valuation allowance for deferred tax assets.

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