Treasury Stock Acquisition (Detail) - USD ($) $ in Thousands	3 Months Ended			6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2021
Schedule of Treasury Stock [Line Items]
Treasury shares at beginning of period				83,402,322
Treasury shares at end of period	83,830,987			83,830,987
Treasury shares at beginning of period				$ 1,366,313
Acquisitions pursuant to long-term incentive plan, cost	$ 3,522	$ 910	$ 20,025
Treasury shares at end of period	$ 1,369,835			$ 1,369,835
Long Term Incentive Plan
Schedule of Treasury Stock [Line Items]
Acquisitions pursuant to long-term incentive plan, shares				428,665
Acquisitions pursuant to long-term incentive plan, cost				$ 3,522