Schedule of Information Related to Stock Repurchase Programs (Detail) - USD ($)		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Jul. 31, 2019	Dec. 31, 2017	Dec. 31, 2014
Class of Stock [Line Items]
Additional dollars authorized for repurchase		$ 2,700,000,000			$ 1,000,000,000.0		$ 1,700,000,000
Aggregate purchase price paid for shares purchased as part of publicly announced program		$ 206,719,000	$ 753,927,000	$ 414,002,000
Stock Repurchase Program
Class of Stock [Line Items]
Total number of shares purchased as part of publicly announced programs		10,671,620
Average price paid per share for shares purchased as part of publicly announced program		$ 122.20
Aggregate purchase price paid for shares purchased as part of publicly announced program		$ 1,304,097,000
Stock Repurchase Programs Twenty Sixteen
Class of Stock [Line Items]
Maximum number of dollars that may yet be purchased under the program						$ 363,660,000
Stock Repurchase Programs Twenty Seventeen
Class of Stock [Line Items]
Additional dollars authorized for repurchase				$ 500,000,000
Total number of shares purchased	[1]			3,435,992
Total number of shares cancelled				11,224
Average price paid per share for forfeited restricted shares				$ 0.01
Aggregate purchase price paid				$ 414,002,000
Maximum number of dollars that may yet be purchased under the program				$ 462,344,000
Stock Repurchase Programs Twenty Seventeen | Stock Repurchase Program
Class of Stock [Line Items]
Total number of shares purchased as part of publicly announced programs				3,321,968
Average price paid per share for shares purchased as part of publicly announced program				$ 120.81
Aggregate purchase price paid for shares purchased as part of publicly announced program				$ 401,316,000
Stock Repurchase Programs Twenty Eighteen
Class of Stock [Line Items]
Additional dollars authorized for repurchase			$ 1,000,000,000
Total number of shares purchased	[1]		5,762,409
Total number of shares cancelled			27,713
Average price paid per share for forfeited restricted shares			$ 0.01
Total number of shares purchased as part of publicly announced programs				3,321,968
Aggregate purchase price paid			$ 753,928,000
Aggregate purchase price paid for shares purchased as part of publicly announced program				$ 401,300,000
Maximum number of dollars that may yet be purchased under the program			$ 756,123,000
Stock Repurchase Programs Twenty Eighteen | Stock Repurchase Program
Class of Stock [Line Items]
Total number of shares purchased as part of publicly announced programs			5,397,753
Average price paid per share for shares purchased as part of publicly announced program			$ 130.84
Aggregate purchase price paid for shares purchased as part of publicly announced program			$ 706,221,000
Stock Repurchase Programs Twenty Nineteen
Class of Stock [Line Items]
Total number of shares purchased	[1]	2,050,735
Total number of shares cancelled		17,779
Average price paid per share for forfeited restricted shares		$ 0.01
Total number of shares purchased as part of publicly announced programs			5,397,753
Aggregate purchase price paid		$ 206,719,000
Aggregate purchase price paid for shares purchased as part of publicly announced program			$ 706,200,000
Maximum number of dollars that may yet be purchased under the program		$ 559,563,000
Stock Repurchase Programs Twenty Nineteen | Stock Repurchase Program
Class of Stock [Line Items]
Total number of shares purchased as part of publicly announced programs		1,951,899
Average price paid per share for shares purchased as part of publicly announced program		$ 100.70
Aggregate purchase price paid for shares purchased as part of publicly announced program		$ 196,560,000
Stock Repurchase Programs Twenty Seventeen to Twenty Nineteen
Class of Stock [Line Items]
Additional dollars authorized for repurchase		$ 1,500,000,000
Total number of shares purchased	[1]	11,249,136
Total number of shares cancelled		56,716
Average price paid per share for forfeited restricted shares		$ 0.01
Aggregate purchase price paid		$ 1,374,649,000

[1] Includes 17,779, 27,713 and 11,224 of restricted shares that were forfeited by former employees pursuant to the terms of our restricted stock purchase plan during 2020, 2019 and 2018, respectively.