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Stock Repurchase Program (Details) (USD $) In Millions, except Per Share data, unless otherwise specified | 1 Months Ended | 6 Months Ended | 20 Months Ended | 0 Months Ended | 3 Months Ended | 7 Months Ended | 20 Months Ended
--- | --- | --- | --- | --- | --- | --- | ---
Aug. 31, 2011 | Mar. 31, 2013 | Mar. 31, 2013 | Aug. 16, 2011 Accelerated Share Repurchase | Sep. 30, 2011 Accelerated Share Repurchase | Mar. 07, 2012 Accelerated Share Repurchase | Mar. 31, 2013 Rule 10b5-1 Repurchase Plan and Open Market Purchases
Stock Repurchase Program |  |  |  |  |  |  |
Authorized amount of stock repurchase | $ 200.0 | $ 1,000.0 |  | $ 100.0 |  |  |
Stock repurchase additional authorized amount |  | 800 |  |  |  |  |
Shares repurchased and retired under the agreement |  |  | 22.2 |  | 4.3 | 4.8 | 17.4
Total cost of shares repurchased under the agreement |  |  | 500.0 |  |  |  | 400.0
Remaining repurchase amount of shares pursuant to the plan |  | $ 500.0 |  |  |  |  |
Average price per share of stock repurchased under the agreement (in dollars per share) |  |  | $ 22.56 |  |  | $ 20.97 | $ 22.99

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- Definition Number of shares that have been repurchased and retired during the period. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 29, 30 -Article 5 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Principles Board Opinion (APB) -Number 12 -Paragraph 10 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Article 3 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21463-112644 + Details
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- Definition Equity impact of the value of stock that has been repurchased and retired during the period. The excess of the purchase price over par value can be charged against retained earnings (once the excess is fully allocated to additional paid in capital). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 29, 30, 31 -Article 5 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Principles Board Opinion (APB) -Number 12 -Paragraph 10 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 04 -Article 3 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21463-112644 + Details
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- Definition Total cost of shares repurchased divided by the total number of shares repurchased. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 30 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6405813&loc=d3e23239-112655 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher AICPA -Name Accounting Research Bulletin (ARB) -Number 43 -Section B -Paragraph 7 -Subparagraph b -Chapter 1 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy. + Details
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