Business and Significant Accounting Policies Business and Significant Accounting Policies (Detail) - New Accounting Pronouncements - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Effective income tax rate reconciliation share-based compensation excess tax benefit amount	$ 10,000
Provision for income taxes	94,849	$ 96,576	$ 90,917
Net income	$ 193,582	$ 175,635	$ 183,766
Basic earnings per share, basic (in Dollars per share)	$ 2.34	$ 2.09	$ 2.06
Diluted earnings per share (in Dollars per share)	$ 2.31	$ 2.06	$ 2.03
Operating cash flow	$ 365,632	$ 345,561	$ 346,779
Cash used by financing activities	(174,686)	(67,690)	(208,670)
Accumulated earnings	$ 1,644,005	1,450,684
Cumulative effect of adoption of ASU No. 2016-09		261
New Accounting Pronouncement, Early Adoption, Effect | Accounting Standards Update 2016-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Basic earnings per share, basic (in Dollars per share)	$ 0.12
Diluted earnings per share (in Dollars per share)	$ 0.12
New Accounting Pronouncement, Early Adoption, Effect | Accounting Standards Update 2016-09, Statutory Tax Withholding Component
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating cash flow	$ 10,000
Cash used by financing activities	(10,000)
Accumulated Earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net income	$ 193,582	175,635	$ 183,766
Cumulative effect of adoption of ASU No. 2016-09		261
Accumulated Earnings | New Accounting Pronouncement, Early Adoption, Effect | Accounting Standards Update 2016-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of adoption of ASU No. 2016-09		$ 300