Employee Benefit Plans (Narrative) (Detail) $ in Thousands	2 Months Ended	3 Months Ended	12 Months Ended
	May 31, 2020	Mar. 31, 2020	Dec. 31, 2020 USD ($) agreement	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Employee Benefit Plan [Line Items]
Percentage of every dollar of a participating employee's pre-tax contributions as matching contribution to 401(k) Plan			100.00%
Number of multiemployer pension plans | agreement			13
Deferred Compensation Plan [Member]
Employee Benefit Plan [Line Items]
Percentage of every dollar of a participating employee's pre-tax contributions as matching contribution to 401(k) Plan	100.00%	100.00%		100.00%	50.00%
Percentage of employee's eligible compensation that represents the maximum amount of employer matching contribution to plan	5.00%	5.00%		5.00%	6.00%
Percentage of salary that may voluntarily be elected to be deferred			80.00%
Percentage of bonuses, commissions and restricted share unit grants that may voluntarily be elected to be deferred			100.00%
Total liability for deferred compensation			$ 43,069	$ 37,707
Voluntary Savings And Investment Plan
Employee Benefit Plan [Line Items]
Total employer expenses, including employer matching contributions			$ 16,350	$ 26,111	$ 12,055
Maximum [Member]
Employee Benefit Plan [Line Items]
Percentage of employee's eligible compensation that represents the maximum amount of employer matching contribution to plan			5.00%
Maximum [Member] | Retirement Savings Plan [Member]
Employee Benefit Plan [Line Items]
Contribution to a deferred profit sharing plan			5.00%