Schedule of Information Related to Stock Repurchase Programs (Detail) - USD ($)		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Feb. 29, 2016	Jul. 31, 2014	Dec. 31, 2013
Class of Stock [Line Items]
Additional dollars authorized for repurchase		$ 800,000,000			$ 400,000,000	$ 400,000,000
Total number of shares purchased	[1]	5,831,987
Total number of shares cancelled		767,704
Average price paid per share for forfeited restricted shares		$ 0.01
Aggregate purchase price paid		$ 671,899,000
Aggregate purchase price paid for shares purchased as part of publicly announced program		$ 346,890,000	$ 224,260,000	$ 100,749,000
Stock Repurchase Program
Class of Stock [Line Items]
Total number of shares purchased as part of publicly announced programs		4,386,991
Average price pad per share for shares purchased as part of publicly announced program		$ 117.19
Aggregate purchase price paid for shares purchased as part of publicly announced program		$ 514,109,000
Stock Repurchase Programs Twenty Thirteen
Class of Stock [Line Items]
Maximum number of shares that may yet be purchased under the program							767,704
Stock Repurchase Programs Twenty Fourteen
Class of Stock [Line Items]
Additional dollars authorized for repurchase				$ 400,000,000
Total number of shares purchased	[1]			1,029,164
Total number of shares cancelled				767,704
Total number of shares purchased as part of publicly announced programs				548,192
Average price pad per share for shares purchased as part of publicly announced program				$ 105.71
Aggregate purchase price paid				$ 100,749,000
Aggregate purchase price paid for shares purchased as part of publicly announced program				57,950,000
Maximum number of dollars that may yet be purchased under the program				$ 342,050,000
Stock Repurchase Programs Twenty Fifteen
Class of Stock [Line Items]
Total number of shares purchased	[1]		1,819,503
Total number of shares purchased as part of publicly announced programs			1,326,207
Average price pad per share for shares purchased as part of publicly announced program			$ 125.34
Aggregate purchase price paid			$ 224,260,000
Aggregate purchase price paid for shares purchased as part of publicly announced program			166,222,000
Maximum number of dollars that may yet be purchased under the program			$ 175,828,000
Stock Repurchase Programs Twenty Sixteen
Class of Stock [Line Items]
Additional dollars authorized for repurchase		$ 400,000,000
Total number of shares purchased	[1]	2,983,320
Average price paid per share for forfeited restricted shares		$ 0.01
Aggregate purchase price paid		$ 346,890,000
Maximum number of dollars that may yet be purchased under the program		$ 285,891,000
Stock Repurchase Programs Twenty Sixteen | Stock Repurchase Program
Class of Stock [Line Items]
Total number of shares purchased as part of publicly announced programs		2,512,592
Average price pad per share for shares purchased as part of publicly announced program		$ 115.39
Aggregate purchase price paid for shares purchased as part of publicly announced program		$ 289,937,000

[1] Includes 2,500 of restricted shares that were forfeited by a former employee pursuant to the terms of our restricted stock purchase plan.