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Stock Option Plans and Share-Based Compensation PSU performance to vesting table by Program year (Details) (USD $)
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3 Months Ended | 12 Months Ended | 3 Months Ended | 0 Months Ended | 12 Months Ended | 3 Months Ended | 0 Months Ended | 3 Months Ended | 12 Months Ended | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
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Mar. 31, 2013
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Mar. 31, 2013
Performance Shares [Member]
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Dec. 31, 2011
Performance Shares [Member]
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Dec. 31, 2012
Performance Shares [Member]
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Mar. 31, 2013
Employee Stock [Member]
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Mar. 31, 2013
PSU program year one [Member]
Performance Shares [Member]
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Mar. 31, 2013
Below the 35th percentile ranking [Member]
PSU Program Year Two [Member]
Performance Shares [Member]
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Mar. 31, 2013
Below 50th percentile ranking [Member]
PSU Program Year Two [Member]
Performance Shares [Member]
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Mar. 31, 2013
At least 50th percentile (after yr one) [Member]
PSU Program Year Two [Member]
Performance Shares [Member]
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Mar. 31, 2013
Minimum [Member]
Below the 75th percentile ranking [Member]
PSU program year one [Member]
Performance Shares [Member]
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Mar. 31, 2013
Maximum [Member]
Below the 75th percentile ranking [Member]
PSU program year one [Member]
Performance Shares [Member]
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Jan. 17, 2012
2011 PSU [Member]
Performance Shares [Member]
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Dec. 31, 2012
2011 PSU [Member]
Performance Shares [Member]
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Mar. 31, 2013
2011 PSU [Member]
Below the 35th percentile ranking [Member]
Performance Shares [Member]
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Mar. 31, 2013
2011 PSU [Member]
Below 50th percentile ranking [Member]
Performance Shares [Member]
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Mar. 31, 2013
2011 PSU [Member]
Below the 65th percentile ranking [Member]
Performance Shares [Member]
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Mar. 31, 2013
2011 PSU [Member]
At or above the 75th percentile ranking [Member]
Performance Shares [Member]
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Jan. 22, 2013
2012 PSU [Member]
Performance Shares [Member]
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Mar. 31, 2013
2012 PSU [Member]
Performance Shares [Member]
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Dec. 31, 2012
2012 PSU [Member]
Performance Shares [Member]
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| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | ||||||||||||||||||||
| Shares, Issued | 4,039,838 | |||||||||||||||||||
| Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number | 281,000 | 175,000 | ||||||||||||||||||
| Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value | $ 14.48 | $ 11.00 | ||||||||||||||||||
| Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period | 138,000 | 100,000 | 10,000 | 125,000 | ||||||||||||||||
| Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value | $ 17.40 | |||||||||||||||||||
| Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period | 16,000 | |||||||||||||||||||
| Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Weighted Average Grant Date Fair Value | $ 15.66 | |||||||||||||||||||
| Percentile ranking of 2011 shareholder return | 76.30% | 35.30% | ||||||||||||||||||
| PSU percentage eligible for time-based vesting | 0.00% | 50.00% | 100.00% | 110.00% | 119.00% | 0.00% | 50.00% | 100.00% | 120.00% | |||||||||||
| PSU percentage eligible for vesting based on actual return | 120.00% | 50.00% | ||||||||||||||||||
| PSU shares eligible for vesting based on actual shareholder return | 120,000 | 120,000 | 62,500 | |||||||||||||||||
| Share-based Compensation Arrangement by Share-based Payment Award, First Year Share Vesting Rate | 25.00% | |||||||||||||||||||
| Share-based Compensation Arrangement by Share-based payment Award, Percent Vested in First Year | 0.00% | |||||||||||||||||||
| Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period | 16,000 | |||||||||||||||||||
| Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeitures, Weighted Average Grant Date Fair Value | $ 0.00 | |||||||||||||||||||
| Common Stock, Capital Shares Reserved for Future Issuance | 1,107,858 | 1,291,717 | ||||||||||||||||||
| Share-based Compensation Arrangement by Share-based Payment Award, Shares Issued in Period | 256,994 | |||||||||||||||||||