Segment Information - Intersegment Activity Eliminated in Arriving at Consolidated Totals was Included in "All Other" Category (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Segment Reporting Information [Line Items]
Revenues	$ 5,954,761	$ 6,191,943	$ 5,928,302
Income taxes	416,369	618,112	590,160
Net income	1,353,152	1,929,149	1,918,080
Intersegment Activity Eliminated in Consolidated Totals [Member]
Segment Reporting Information [Line Items]
Revenues	(47,604)	(48,559)	(41,285)
Expenses	(14,038)	(18,218)	(24,660)
Income taxes	(8,824)	(7,976)	(4,371)
Net income	$ (24,742)	$ (22,365)	$ (12,254)