Represents the expense recognized during the period arising from share-based compensation arrangements (for example, shares of stock, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 123R
-Paragraph 64
-Subparagraph b

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 123R
-Paragraph A240
-Subparagraph g(1)

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Staff Accounting Bulletin (SAB)
-Number Topic 14
-Section F

Stock-based Compensation and Equity (Details) (USD $)	3 Months Ended		6 Months Ended		1 Months Ended		3 Months Ended			6 Months Ended
Stock-based Compensation and Equity (Details) (USD $)	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010	Jan. 31, 2011 RSU January 2011 [Member]	Jan. 31, 2011 Performance Stock Units PSU [Member]	Mar. 31, 2011 RSU March 2011 [Member]	Mar. 31, 2011 PSU March 2011 [Member]	Jun. 30, 2011 RSU June 2011 [Member]	Jun. 30, 2011 RSU June 2011 Additional [Member]
Share Based Arrangements To Obtain Goods And Services [Abstract]
Share-based Compensation	$ 6,200,000	$ 2,500,000	$ 8,628,000	$ 4,936,000
Employee Service Share Based Compensation Tax Benefit From Compensation Expense	2,800,000	1,100,000	3,900,000	2,200,000
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share Based Compensation Arrangement By Share Based Payment Award Number Of Shares Authorized					178,550	191,600	160,000	120,000	60,000	86,000
Share Based Compensation Arrangement By Share Based Payment Award Award Vesting Period					three years		four years	three years	one to five years	over three years
Maximum Share-based Compensation Expense			29,700,000
Allocated Share-based Compensation Expense	1,600,000		2,600,000
Earnings Per Share Reconciliation Abstract
Net Income (Loss) Attributable to Parent	79,112,000	23,432,000	102,455,000	37,845,000
Allocation of distribution equivalents paid on unvested restricted stock units in excess of net income	(1,166,000)	(453,000)	(1,510,000)	(783,000)
Net Income Loss Available To Common Stockholders Basic	77,946,000	22,979,000	100,945,000	37,062,000
Dilutive Securities	1,000	233,000	333,000	331,000
Net Income Loss Available To Common Stockholders Diluted	77,947,000	23,212,000	101,278,000	37,393,000
Basic	39,782,796	39,081,064	39,760,676	39,116,126
Effect of dilutive securities	460,752	429,167	431,742	451,457
Diluted	40,243,548	39,510,231	40,192,418	39,567,583
Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount	100,000	900,000	100,000	900,000
PSU Revised Compensation Expense			$ 2,400,000