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Share Repurchases (Notes) | 9 Months Ended
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Sep. 30, 2017
Equity, Class of Treasury Stock [Line Items] |
Treasury Stock [Text Block] | In July 1998, the company's Board of Directors adopted a stock repurchase program and subsequently authorized the purchase of common shares in open market purchases. During 2013, the company's Board of Directors authorized the purchase of additional common shares in open market purchases. For the three months period ended September 30, 2017 the company repurchased 1,680,395 shares of its common stock under the program for $200.4 million, including applicable commissions, which represented an average price of $119.23. As of September 30, 2017, the total number of shares authorized for repurchase under the program is 4,570,266. As of September 30, 2017, 3,860,996 shares had been purchased under the 1998 stock repurchase program.

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- Definition The entire disclosure for treasury stock, including, but not limited to, average cost per share, description of share repurchase program, shares repurchased, shares held for each class of treasury stock. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 30 -URI http://asc.fasb.org/subtopic&trid=2208821 + Details
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