Treasury Stock Acquisition (Detail) - USD ($) $ in Thousands	3 Months Ended					9 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2021
Schedule of Treasury Stock [Line Items]
Treasury shares at beginning of period						83,402,322
Treasury shares at end of period	83,836,546					83,836,546
Treasury shares at beginning of period						$ 1,366,313
Acquisitions pursuant to long-term incentive plan, cost	$ 52	$ 3,522	$ 194	$ 910	$ 20,025
Treasury shares at end of period	$ 1,369,887					$ 1,369,887
Long Term Incentive Plan
Schedule of Treasury Stock [Line Items]
Acquisitions pursuant to long-term incentive plan, shares						434,224
Acquisitions pursuant to long-term incentive plan, cost						$ 3,574