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Treasury Stock - Additional Information (Detail) (USD $)
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3 Months Ended | 9 Months Ended | |||
|---|---|---|---|---|---|
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Sep. 30, 2012
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Dec. 31, 2011
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Sep. 30, 2012
Two Thousand Five Share Repurchase Program
Class A
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Sep. 30, 2012
Two Thousand Five Share Repurchase Program
Class A
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Sep. 30, 2012
Two Thousand Five Share Repurchase Program
Class A
Maximum
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| Equity, Class of Treasury Stock | |||||
| Stock authorized to repurchase by Board of Directors | $ 800,000,000 | ||||
| Repurchase of treasury stock, shares | |||||
| Treasury stock, shares | 6,405,000 | 6,405,000 | 3,826,947 | 3,826,947 | |
| Shares repurchased, average price per share | $ 90.23 | $ 90.23 | |||
| Treasury stock, cost | $ 475,184,000 | $ 475,184,000 | $ 345,300,000 | $ 345,300,000 | |