Treasury Stock Acquisition (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Schedule of Treasury Stock [Line Items]
Treasury shares at beginning of period	53,701,096
Treasury shares at end of period	59,109,468
Treasury shares at beginning of period	$ 1,080,448
Treasury stock acquired, cost	75,113	$ 16,928
Treasury shares at end of period	$ 1,155,561
Stock Buyback Program
Schedule of Treasury Stock [Line Items]
Treasury stock acquired, shares	5,408,132
Treasury stock acquired, cost	$ 75,110
Long Term Incentive Plan
Schedule of Treasury Stock [Line Items]
Treasury stock acquired, shares	240
Treasury stock acquired, cost	$ 3