Income Taxes (Narrative) (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Income Tax Disclosure [Abstract]
Effective income tax rates	25.30%	24.60%	24.50%	22.50%
Liability for income taxes associated with uncertain tax positions	$ 7,700		$ 7,700		$ 7,200
Offsetting tax benefits related to uncertain tax positions	$ 2,700		2,700		2,100
Other tax benefits related to interest and penalties of uncertain tax positions			$ 0		$ 0
Unrecognized tax positions increase decrease, months			It is reasonably possible that the amount of the unrecognized benefit with respect to certain of the Company’s unrecognized tax positions may increase or decrease within the next 12 months.  Any such change may be the result of ongoing audits or the expiration of federal and state statutes of limitations for the assessment of taxes.