Condensed Consolidated Statements of Changes in Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Treasury Stock [Member]	AOCI Attributable to Parent [Member]	Noncontrolling Interest [Member]
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest at Oct. 31, 2017	$ 4,537,090	$ 1,779	$ 720,115	$ 4,474,064	$ (662,854)	$ (1,910)	$ 5,896
Net income	437,175			437,175
Purchase of treasury stock	(427,526)				(427,526)
Exercise of stock options and stock based compensation issuances	8,848		(19,998)		28,846
Employee stock purchase plan issuances	880		92		788
Stock-based compensation	21,879		21,879
Dividends declared	(45,761)			(45,761)
Other comprehensive income	512					512
Net Income (Loss) Attributable to Noncontrolling Interest	(3)						(3)
Capital contributions	2,823						2,823
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest at Jul. 31, 2018	4,537,380	1,779	722,461	4,866,980	(1,060,746)	(1,810)	8,716
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest at Apr. 30, 2018	4,486,596	1,779	715,949	4,690,272	(925,317)	(1,980)	5,893
Net income	193,258			193,258
Purchase of treasury stock	(136,048)				(136,048)
Exercise of stock options and stock based compensation issuances	311		(14)		325
Employee stock purchase plan issuances	288		(6)		294
Stock-based compensation	6,532		6,532
Dividends declared	(16,550)			(16,550)
Other comprehensive income	170					170
Capital contributions	2,823						2,823
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest at Jul. 31, 2018	4,537,380	1,779	722,461	4,866,980	(1,060,746)	(1,810)	8,716
Cumulative effect adjustment upon adoption of new accounting pronouncements	1,463		373	1,502		(412)
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest at Oct. 31, 2018	4,768,912	1,779	727,053	5,161,551	(1,130,878)	694	8,713
Net income	387,692			387,692
Purchase of treasury stock	(167,474)				(167,474)
Exercise of stock options and stock based compensation issuances	4,461		(21,951)		26,412
Employee stock purchase plan issuances	976		(42)		1,018
Stock-based compensation	19,351		19,351
Dividends declared	(48,301)			(48,301)
Other comprehensive income	168					168
Net Income (Loss) Attributable to Noncontrolling Interest	(5)						(5)
Capital contributions	36,664						36,664
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest at Jul. 31, 2019	4,984,457	1,779	724,411	5,482,955	(1,270,922)	862	45,372
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest at Apr. 30, 2019	4,986,240	1,779	721,311	5,352,424	(1,135,166)	806	45,086
Net income	146,318			146,318
Purchase of treasury stock	(142,230)				(142,230)
Exercise of stock options and stock based compensation issuances	3,883		(2,284)		6,167
Employee stock purchase plan issuances	256		(51)		307
Stock-based compensation	5,435		5,435
Dividends declared	(15,787)			(15,787)
Other comprehensive income	56					56
Net Income (Loss) Attributable to Noncontrolling Interest	(1)						(1)
Capital contributions	287						287
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest at Jul. 31, 2019	4,984,457	1,779	724,411	5,482,955	(1,270,922)	862	45,372
Cumulative effect adjustment upon adoption of new accounting pronouncements	$ (17,987)			$ (17,987)