v2.4.0.6
Employee Benefit Plans (Details 2) (USD $)
In Millions, except Share data, unless otherwise specified
 12 Months Ended
Dec. 31, 2011
Y
Dec. 31, 2010
Dec. 31, 2009
Restricted stock unit and restricted stock activity      
Number of Restricted Stock Units and Shares of Restricted Stock, Unissued, Beginning Balance 849,300 653,200 236,200
Restricted stock awarded to executives, other officers and directors 179,200 367,900 516,000
Number of Restricted Stock Units and Shares of Restricted Stock, Vested and Issued (250,500) (171,800) (67,000)
Number of Restricted Stock Units and Shares of Restricted Stock, Forfeited (8,000) 0 (32,000)
Number of Restricted Stock Units and Shares of Restricted Stock, Unissued, Ending Balance 770,000 849,300 653,200
Number of Restricted Stock Units and Shares of Restricted Stock, Vested and Unissued 396,100    
Weighted Average Grant Date Fair Value per Share, Unissued, Beginning Balance $ 26.39 $ 23.85 $ 23.50
Weighted Average Grant Date Fair Value per Share, Granted $ 29.97 $ 29.14 $ 23.92
Weighted Average Grant Date Fair Value per Share, Vested and Issued $ 26.61 $ 22.63 $ 23.28
Weighted Average Grant Date Fair Value per Share, Forfeited $ 24.97 $ 0.00 $ 23.50
Weighted Average Grant Date Fair Value per Share, Unissued, Ending Balance $ 27.17 $ 26.39 $ 23.85
Weighted Average Grant Date Fair Value per Share, Vested and Unissued $ 26.88    
Weighted Average Remaining Contractual Term (years), Unissued 0.4    
Aggregate Intrinsic Value, Unissued $ 21.2