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]	Cumulative Effect, Period of Adoption, Adjustment	Cumulative Effect, Period of Adoption, Adjustment Retained Earnings [Member]
Total equity	$ 5,118,693	$ 1,529	$ 726,879	$ 4,774,422	$ (425,183)	$ (5,831)	$ 46,877
Stockholders' Equity, Other								$ 0
Net income	132,546			132,546
Purchase of treasury stock	(633,553)				(633,553)
Exercise of stock options and stock based compensation issuances	4,573		(17,828)		22,401
Employee stock purchase plan issuances	729		(607)		1,336
Stock-based compensation	16,802		16,802
Dividends declared	(28,951)			(28,951)
Other Comprehensive Income (Loss), Net of Tax	556					556
Net Income (Loss) Attributable to Noncontrolling Interest	(8)						(8)
Capital contributions	2,335						2,335
Total equity	4,705,080	1,529	723,109	4,816,286	(879,820)	(5,553)	49,529
Net income	75,670			75,670
Purchase of treasury stock	(157,529)				(157,529)
Exercise of stock options and stock based compensation issuances	643		(716)		1,359
Employee stock purchase plan issuances	425		(566)		991
Stock-based compensation	3,419		3,419
Dividends declared	(13,939)			(13,939)
Other Comprehensive Income (Loss), Net of Tax	278					278
Net Income (Loss) Attributable to Noncontrolling Interest	(7)						(7)
Capital contributions	(318)						(318)
Total equity	4,613,722	1,529	725,246	4,878,017	(1,034,999)	(5,275)	49,204
Total equity	4,927,476	1,529	717,272	5,164,086	(1,000,454)	(7,198)	52,241
Stockholders' Equity, Other								(595)
Stockholders' Equity, Other | Accounting Standards Update 2016-13								$ (600)	$ (595)
Net income	224,365			224,365
Purchase of treasury stock	(179,648)				(179,648)
Exercise of stock options and stock based compensation issuances	6,863		(24,235)		31,098
Employee stock purchase plan issuances	704		106		598
Stock-based compensation	16,279		16,279
Dividends declared	(35,283)			(35,283)
Other Comprehensive Income (Loss), Net of Tax	5,150					5,150
Net Income (Loss) Attributable to Noncontrolling Interest	(20)						(20)
Capital contributions	(4,502)						(4,502)
Total equity	4,834,492	1,529	708,668	5,245,935	(1,162,811)	(6,486)	47,657
Net income	127,866			127,866
Purchase of treasury stock	(253)				(253)
Exercise of stock options and stock based compensation issuances	11,632		(2,790)		14,422
Employee stock purchase plan issuances	334		98		236
Stock-based compensation	3,446		3,446
Dividends declared	(21,228)			(21,228)
Other Comprehensive Income (Loss), Net of Tax	4,438					4,438
Net Income (Loss) Attributable to Noncontrolling Interest	1						1
Capital contributions	61						61
Total equity	$ 4,960,789	$ 1,529	$ 709,422	$ 5,352,573	$ (1,148,406)	$ (2,048)	$ 47,719