Condensed Consolidated Statement of Shareholders' Equity Statement - USD ($) shares in Thousands, $ in Thousands		Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	AOCI Attributable to Parent [Member]
Common Stock, Shares, Outstanding		282,912
Stockholders' Equity, Other		$ 2,197,745	$ 283		$ 2,207,053	$ (9,591)
Stockholders' Equity, Other		1,985,698	$ 283		1,997,207	(11,792)
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest		79,519			79,519
Other Comprehensive Income (Loss), Net of Tax		(1,902)				(1,902)
Shares of common stock repurchased			(3,146)
Value of common stock repurchased		(152,246)	$ 1	$ 60,515	91,730	0
Stock Issued During Period, Shares, Restricted Stock Award, Net of Forfeitures			519
Stock Issued During Period, Value, Restricted Stock Award, Net of Forfeitures		(11,520)	$ 0	(11,520)	0	0
Stock Issued During Period, Shares, Other			737
Stock Issued During Period, Value, Stock Options Exercised		18,669	$ 1	18,668	0	0
Adjustments to Additional Paid in Capital, Share-based Compensation, Requisite Service Period Recognition		38,392	$ 0	38,392	0	0
Stock Issued During Period, Shares, Employee Stock Purchase Plans			416
Stock Issued During Period, Value, Employee Stock Ownership Plan			$ 0
Stock Issued During Period, Value, Employee Stock Purchase Plan		14,975		14,975	0	0
Dividends, Common Stock, Cash		(202,883)	$ 0	0	(202,883)	0
Stockholders' Equity, Other		1,930,940			1,945,646	(14,985)
Common Stock, Shares, Outstanding			281,731
Stockholders' Equity, Other			$ 283			(11,792)
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest		(75,015)			(75,015)
Other Comprehensive Income (Loss), Net of Tax		(2,201)				(2,201)
Shares of common stock repurchased			(1,488)
Value of common stock repurchased		(76,954)	$ 1	43,543	33,410	0
Stock Issued During Period, Shares, Restricted Stock Award, Net of Forfeitures			258
Stock Issued During Period, Value, Restricted Stock Award, Net of Forfeitures		(6,104)	$ 0	(6,104)	0	0
Stock Issued During Period, Shares, Other			521
Stock Issued During Period, Value, Stock Options Exercised		13,508	$ 1	13,507	0	0
Adjustments to Additional Paid in Capital, Share-based Compensation, Requisite Service Period Recognition		21,165	$ 0	21,165	0	0
Stock Issued During Period, Shares, Employee Stock Purchase Plans			416
Stock Issued During Period, Value, Employee Stock Ownership Plan			$ 0
Stock Issued During Period, Value, Employee Stock Purchase Plan		14,975		14,975	0	0
Dividends, Common Stock, Cash		$ (101,421)	0	0	(101,421)	0
Common Stock, Shares, Outstanding		281,438
Common Stock, Shares, Outstanding		278,664
Stockholders' Equity, Other		$ 1,912,323	279		1,924,764	(12,720)
Stockholders' Equity, Other		1,755,414	$ 279		1,766,471	(11,336)
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest		329,315			329,315
Other Comprehensive Income (Loss), Net of Tax		3,649
Shares of common stock repurchased			(5,822)
Value of common stock repurchased		(320,056)	$ 0	63,744	256,312	0
Stock Issued During Period, Shares, Restricted Stock Award, Net of Forfeitures			578
Stock Issued During Period, Value, Restricted Stock Award, Net of Forfeitures		(13,444)	$ 0	(13,444)	0	0
Stock Issued During Period, Shares, Other			522
Stock Issued During Period, Value, Stock Options Exercised		13,843	$ 0	13,843	0	0
Adjustments to Additional Paid in Capital, Share-based Compensation, Requisite Service Period Recognition		42,185	$ 0	42,185	0	0
Modification Of Liability Instruments To Equity	[1]			3,471
Stock Issued During Period, Shares, Employee Stock Purchase Plans			0
Stock Issued During Period, Value, Employee Stock Ownership Plan			$ 0
Stock Issued During Period, Value, Employee Stock Purchase Plan		17,689		17,689	0	0
Dividends, Common Stock, Cash		(254,665)	$ 0	0	(254,665)	0
Common Stock, Shares, Outstanding			277,430
Stockholders' Equity, Other		1,755,414	$ 279		1,766,471	(11,336)
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest		131,892
Other Comprehensive Income (Loss), Net of Tax		1,384
Shares of common stock repurchased			(3,960)
Value of common stock repurchased		(207,558)	$ 0	44,181	163,377	0
Stock Issued During Period, Shares, Restricted Stock Award, Net of Forfeitures			281
Stock Issued During Period, Value, Restricted Stock Award, Net of Forfeitures		(5,916)	$ 0	(5,916)	0	0
Stock Issued During Period, Shares, Other			191
Stock Issued During Period, Value, Stock Options Exercised		7,235	$ 0	7,235	0	0
Adjustments to Additional Paid in Capital, Share-based Compensation, Requisite Service Period Recognition		21,702	$ 0	21,702	0	0
Modification Of Liability Instruments To Equity	[1]			3,471
Stock Issued During Period, Shares, Employee Stock Purchase Plans			0
Stock Issued During Period, Value, Employee Stock Ownership Plan			$ 0
Stock Issued During Period, Value, Employee Stock Purchase Plan		17,689		17,689	0	0
Dividends, Common Stock, Cash		$ (126,808)	$ 0	$ 0	(126,808)	$ 0
Common Stock, Shares, Outstanding		273,942
Cumulative Effect of New Accounting Principle in Period of Adoption		$ 2,487			$ 2,487

[1] (1) In December 2018, $3.5 million was reclassified from accrued salaries to additional paid-in capital due to a settlement agreement relating to the expiration of stock options.