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Organization And Operations Of The Company (Details) (USD $) | 12 Months Ended |  | 1 Months Ended |
--- | --- | --- | --- | ---
Dec. 31, 2010 | Dec. 31, 2011 | Jun. 22, 2010 OAS Holding Company LLC [Member] | Jun. 22, 2010 IPO [Member]
Organization And Operations Of The Company [Line Items] |  |  |  |
Sale of common stock | 92,240,345 | 92,483,393 | 17,930,000 | 30,370,000
Sale of common stock price per share | $ 0.01 | $ 0.01 | $ 14 | $ 14.00
Underwriting discounts and commissions |  |  |  | $ 25,500,000
Proceeds from issuance of initial public offering | $ 399,669,000 |  | $ 236,000,000 |

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- Definition Face amount or stated value of common stock per share; generally not indicative of the fair market value per share. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 30 -Article 5 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 129 -Paragraph 4 -LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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 FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.29) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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