Stock-based Compensation and Equity (Details) (USD $)	3 Months Ended		9 Months Ended		1 Months Ended		3 Months Ended			9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 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]	Sep. 30, 2011 RSU June 2011 [Member]	Sep. 30, 2011 RSU June 2011 Additional [Member]
Share Based Arrangements To Obtain Goods And Services [Abstract]
Share-based Compensation	$ 4,400,000	$ 1,800,000	$ 13,026,000	$ 6,695,000
Employee Service Share Based Compensation Tax Benefit From Compensation Expense	1,900,000	800,000	5,800,000	2,900,000
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			29,600,000
Allocated Share-based Compensation Expense	2,600,000		5,700,000
Earnings Per Share Reconciliation Abstract
Net Income (Loss) Attributable to Parent	25,202,000	16,346,000	129,988,000	54,191,000
Allocation of distribution equivalents paid on unvested restricted stock units in excess of net income	(371,000)	(116,000)	(1,914,000)	(348,000)
Net Income Loss Available To Common Stockholders Basic	24,831,000	16,230,000	128,074,000	53,843,000
Dilutive Securities	355,000	66,000	695,000	398,000
Net Income Loss Available To Common Stockholders Diluted	25,186,000	16,296,000	128,769,000	54,241,000
Basic	39,861,064	39,180,719	39,794,506	39,161,086
Effect of dilutive securities	543,456	537,212	629,810	613,036
Diluted	40,404,520	39,717,931	40,424,316	39,774,122
Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount		1,045,700		920,273
PSU Revised Compensation Expense			2,400,000
Director Maximum Number Of Shares Issuance			325,000
Value Per Director Old	50,000		50,000
Value Per Director New	70,000		70,000
Additional Director Shares Issued			17,335
Director Compensation Expense			$ 700,000