Condensed Consolidated Statements of Shareholders' Equity (USD $) In Thousands, except Share data	Common Stock	Capital Surplus	Retained Earnings	Accumulated Other Comprehensive Income/(Loss)	Common Stock in Treasury	Total
Balance, value at Dec. 31, 2009	$ 541	$ 154,495	$ 1,006,903	$ (10,093)	$ (995,261)	$ 156,585
Balance, shares at Dec. 31, 2009	54,069,000				(18,623,000)
Net income			183,491			183,491
Other comprehensive income:
Prior service costs, net of income tax				8		8
Net actuarial pension loss, net of income tax				460		460
Unrealized gain (loss)				70		70
Comprehensive income						184,029
Exercise of stock options and equity awards, value			(8,191)		10,811	2,620
Exercise of stock options and equity awards, shares					106,000
Tax benefit from exercise of stock options and equity award vesting		2,184				2,184
Stock-based compensation		8,999				8,999
Common shares repurchased, value					(200,059)	(200,059)
Common shares repurchased, shares					(1,953,000)	(1,952,500)
Issuance of shares for Directors' compensation, value			1		29	30
Issuance of shares for Directors' compensation, shares					1,000
Shares tendered for taxes, value					(956)	(956)
Shares tendered for taxes, shares					(9,000)
Balance, value at Jun. 30, 2010	541	165,678	1,182,204	(9,555)	(1,185,436)	153,432
Balance, shares at Jun. 30, 2010	54,069,000				(20,478,000)
Balance, value at Mar. 31, 2010
Net income			190,675			190,675
Other comprehensive income:
Prior service costs, net of income tax				6,332		6,332
Net actuarial pension loss, net of income tax				(1,320)		(1,320)
Unrealized gain (loss)				34		34
Comprehensive income						195,721
Exercise of stock options and equity awards, value			(5,440)		10,713	5,273
Exercise of stock options and equity awards, shares					108,000
Tax benefit from exercise of stock options and equity award vesting		1,443				1,443
Stock-based compensation		6,814				6,814
Common shares repurchased, value					(234,597)	(234,597)
Common shares repurchased, shares					(3,705,000)
Shares tendered for taxes, value					(16)	(16)
Shares tendered for taxes, shares					(1,000)
Common shares retired, value	(170)		(842,761)		842,931	0
Common shares retired, shares	(17,000,000)				17,000,000
Balance, value at Dec. 31, 2010	371	173,935	524,678	(4,509)	(566,405)	128,070
Balance, shares at Dec. 31, 2010	37,069,000				(7,076,000)
Net income			164,386			164,386
Other comprehensive income:
Prior service costs, net of income tax				(422)		(422)
Net actuarial pension loss, net of income tax				580		580
Unrealized gain (loss)				(87)		(87)
Comprehensive income						164,457
Exercise of stock options and equity awards, value			(4,160)		9,143	4,983
Exercise of stock options and equity awards, shares					138,000
Tax benefit from exercise of stock options and equity award vesting		989				989
Stock-based compensation		7,030				7,030
Common shares repurchased, value					(218,520)	(218,520)
Common shares repurchased, shares					(3,100,000)	(3,100,000)
Issuance of shares for Directors' compensation, value			1		29	30
Issuance of shares for Directors' compensation, shares					1,000
Shares tendered for taxes, value					(564)	(564)
Shares tendered for taxes, shares					(9,000)
Balance, value at Jun. 30, 2011	$ 371	$ 181,954	$ 684,905	$ (4,438)	$ (776,317)	$ 86,475
Balance, shares at Jun. 30, 2011	37,069,000				(10,046,000)