Stock Awards (Details)	3 Months Ended	12 Months Ended
Mar. 31, 2012	Dec. 31, 2011
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Reserved shares of common stock for awards under the Equity Incentive Plan	7,441,180
Common stock remaining for future stock awards	1,438,541
Stock awards vesting period in years	two
Time-Based Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation, shares issued	275,464	292,803
Stock awards vesting period in years	three
Performance-Based Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation, shares issued	252,566	253,655
Stock awards vesting period in years	three
Multi-Year Performance-Based Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation, multi-year performance-based awards	649,793	600,000
Stock awards vesting period in years	three

The maximum number of shares (or other type of equity) originally approved (usually by shareholders and board of directors), net of any subsequent amendments and adjustments, for awards under the equity-based compensation plan. As stock or unit options and equity instruments other than options are awarded to participants, the shares or units remain authorized and become reserved for issuance under outstanding awards (not necessarily vested).

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Other than shares newly issued, the number of additional shares issued (for example, a stock split) or canceled (for example, to correct a share issuance), during the period under the plan.

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- Definition

The number of shares newly issued during the reporting period under the plan.

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