Income Taxes (Narrative) (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Income Taxes [Line Items]
Valuation allowance	$ 0	$ 0
Tax benefit due to change in tax rate	3,500,000
Interest and penalties related to unrecognized tax benefits	200,000	200,000
Unrecognized tax benefits accrued interest and penalties	500,000	300,000
Total unrecognized tax benefits and accrued interest and penalties	6,100,000	$ 5,900,000
Unrecognized tax benefits if recognized will would affect tax rate	6,100,000
State and Local Jurisdiction
Income Taxes [Line Items]
Disallowed carryforwards	$ 550,800,000