Net Income Per Share - Contingently Issuable Equity Awards (Details) (Contingently Issuable Shares [Member]) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Contingently Issuable Equity Awards Excluded from Computation of Earnings Per Share [Line Items]
Contingently issuable equity awards	716	1,606
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	716	806
Stock Appreciation Rights (SARs) [Member]
Contingently Issuable Equity Awards Excluded from Computation of Earnings Per Share [Line Items]
Contingently issuable equity awards	0	800