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Stockholders' Equity and Earnings Per Common Share - Additional Information (Detail) (USD $) In Millions, except Share data, unless otherwise specified | 3 Months Ended | 12 Months Ended
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Mar. 31, 2013 | Mar. 31, 2012 | Mar. 31, 2013 Share Repurchase Program Expire In January 2014 [Member] | Jun. 30, 2012 Share Repurchase Program Expire In January 2014 [Member] | Mar. 31, 2013 Share Repurchase Program Expire In August 2012 [Member] | Mar. 31, 2011 Share Repurchase Program Expire In August 2012 [Member] | Mar. 31, 2013 shares repurchased on the open market [Member] | Mar. 31, 2012 shares repurchased on the open market [Member] | Dec. 31, 2012 shares repurchased on the open market [Member]
Stockholders Equity Note [Line Items] |  |  |  |  |  |  |  |  |
Oustanding Stock Options, grant price range, lower limit | $ 11.37 |  |  |  |  |  |  |  |
Oustanding Stock Options, grant price range, upper limit | $ 26.29 |  |  |  |  |  |  |  |
Outstanding Nonvested stock awards, grant prices range, lower limit | $ 19.38 |  |  |  |  |  |  |  |
Outstanding Nonvested stock awards, grant prices range, upper limit | $ 26.31 |  |  |  |  |  |  |  |
Antidilutive common shares not included in the computation of dilutive earnings per share | 400,000 | 2,200,000 |  |  |  |  |  |  |
Stock Repurchase Program, Authorized Amount |  |  |  | $ 750.0 |  | $ 1,000.0 |  |  |
Stock Repurchase Program Remaining Authorized Repurchase Amount |  |  | $ 454.9 |  | $ 0 |  |  |  |
Treasury Stock, Shares, Acquired |  |  |  |  |  |  | 3,700,000 | 7,500,000 | 23,600,000
Preferred stock, authorized | 25,000,000 |  |  |  |  |  |  |  |
Preferred stock, par value | $ 0.10 |  |  |  |  |  |  |  |
Preferred stock, issued | 0 |  |  |  |  |  |  |  |

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