Net Income Per Share - Contingently Issuable Equity Awards (Details) (Contingently Issuable Shares [Member]) In Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Contingently Issuable Equity Awards Excluded from Computation of Earnings Per Share [Line Items]
Contingently issuable equity awards	1,690	1,508	1,690	1,508
Options to Purchase Shares of Common Stock and Restricted Stock Awards [Member]
Contingently Issuable Equity Awards Excluded from Computation of Earnings Per Share [Line Items]
Contingently issuable equity awards	890	708	890	708
Stock Appreciation Rights (SARs) [Member]
Contingently Issuable Equity Awards Excluded from Computation of Earnings Per Share [Line Items]
Contingently issuable equity awards	800	800	800	800