Consolidated Statements Of Shareholders' Equity (USD $) In Thousands	Total	Common Stock [Member]	Additional Paid-In Capital [Member]	Accumulated Other Comprehensive Income [Member]	Retained Earnings (Accumulated Deficit) [Member]
Shareholders' Equity beginning of period at Dec. 31, 2012	$ 2,189,616	$ 3,866	$ 3,030,889	$ (992)	$ (844,147)
Shareholders' Equity, shares beginning of period at Dec. 31, 2012		386,608
Stock option exercises	18,544	14	18,530	0	0
Stock option exercises, shares		1,357
Stock awards, net of cancellations		7	(7)
Stock awards, net of cancellations, shares		719
Stock repurchases	(6,447)	(3)	(2,593)		(3,851)
Stock repurchases, shares		(331)
Stock-based compensation	8,127	0	8,127	0	0
Share-based compensation, shares
Net income	118,179				118,179
Other comprehensive income	196			196
Shareholders' Equity end of period at Jun. 30, 2013	2,328,215	3,884	3,054,946	(796)	(729,819)
Shareholders' Equity, shares end of period at Jun. 30, 2013		388,353
Shareholders' Equity beginning of period at Dec. 31, 2013	4,648,952	3,813	3,052,016	(795)	1,593,918
Shareholders' Equity, shares beginning of period at Dec. 31, 2013		381,300
Stock option exercises	5,789	5	5,784	0	0
Stock option exercises, shares		532
Stock awards, net of cancellations		(1)	1
Stock awards, net of cancellations, shares		(68)
Cash dividends declared	(37,979)				(37,979)
Stock repurchases	(103,711)	(53)			(103,658)
Stock repurchases, shares		(5,311)
Stock-based compensation	8,893	0	8,874	0	19
Share-based compensation, shares
Excess tax benefits (deficiencies) from share-based awards	(660)		(660)
Net income	116,699				116,699
Other comprehensive income	61			61
Shareholders' Equity end of period at Jun. 30, 2014	$ 4,638,044	$ 3,764	$ 3,066,015	$ (734)	$ 1,568,999
Shareholders' Equity, shares end of period at Jun. 30, 2014		376,453