Schedule of Impact of Adoption on Consolidated Statements of Income (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disaggregation Of Revenue [Line Items]
Net Revenue before provision for doubtful accounts										$ 11,278,942	$ 10,507,788
Less: Provision for doubtful accounts										869,077	741,578
Net revenues	$ 2,754,496	$ 2,648,913	$ 2,681,353	$ 2,687,516	$ 2,642,787	$ 2,541,864	$ 2,612,356	$ 2,612,858	$ 10,772,278	10,409,865	9,766,210
Other operating expenses									2,614,687	$ 2,493,062	$ 2,359,339
Balances Without Adoption ASC 606 | ASU 2014-09
Disaggregation Of Revenue [Line Items]
Net Revenue before provision for doubtful accounts									11,846,088
Less: Provision for doubtful accounts									1,088,267
Net revenues									10,757,821
Other operating expenses									2,600,230
Effect of Change | ASU 2014-09
Disaggregation Of Revenue [Line Items]
Net revenues									14,457
Other operating expenses									$ 14,457