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Stockholders' Equity - Summary of Shares Repurchased Under Stock Purchase Program (Detail) (USD $) | 3 Months Ended | 6 Months Ended
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Jun. 30, 2013 | Jun. 30, 2012 | Jun. 30, 2013 | Jun. 30, 2012
Summary Of Shares Repurchased Under Stock Purchase Program [Abstract] |  |  |  |
Number of shares repurchased | 17,191 | 6,787 | 40,241 | 6,787
Average price of shares repurchased | $ 40.83 | $ 37.70 | $ 40.88 | $ 37.70
Shares remaining to be repurchased | 194,723 | 234,964 | 194,723 | 234,964

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- Definition Number of stock bought back by the entity at the exercise price or redemption price. + References Reference 1: 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 The remaining number of shares authorized to be repurchased by an entity's Board of Directors under a stock repurchase plan. + References No definition available. + 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 + Details
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