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Summary of Significant Accounting Policies Significant Accounting Policies (Details) (USD $) | 1 Months Ended | 12 Months Ended
--- | --- | ---
Feb. 28, 2014 | Dec. 31, 2014 | Dec. 31, 2013 | Dec. 31, 2012
Summary of Significant Accounting Policies [Line Items] |  |  |  |
Inducement grants - Feb 2014 | 308,250pro_InducementgrantsFeb2014 |  |  |
Tangible Asset Impairment Charges |  | $ 4,040,000us-gaap_TangibleAssetImpairmentCharges | $ 0us-gaap_TangibleAssetImpairmentCharges | $ 0us-gaap_TangibleAssetImpairmentCharges
percentage of total revenue |  | 100.00%pro_PercentageOfTotalRevenue | 100.00%pro_PercentageOfTotalRevenue | 100.00%pro_PercentageOfTotalRevenue
Total shareholder return period, in years, for vesting of MSUs |  | three |  |
Shares issuable upon vesting of MSUs, maximum |  | 200.00%pro_SharesIssuableUponVestingOfMsusMaximum |  |
Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized |  | $ 45,600,000us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized |  |
Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized, Period for Recognition |  | 2 years 5 months 0 days |  |
Term License [Member] |  |  |  |
Summary of Significant Accounting Policies [Line Items] |  |  |  |
percentage of total revenue |  | 2.90%pro_PercentageOfTotalRevenue / pro_RevenueComponentAxis = pro_TermLicenseMember | 3.60%pro_PercentageOfTotalRevenue / pro_RevenueComponentAxis = pro_TermLicenseMember | 4.80%pro_PercentageOfTotalRevenue / pro_RevenueComponentAxis = pro_TermLicenseMember

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- Definition Inducement grants - Feb 2014 + References No definition available. + Details
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- Definition percentage of total revenue + References No definition available. + Details
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- Definition Maximum number of shares issuable upon vesting of MSUs initially granted. + References No definition available. + Details
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- Definition Total shareholder return period used to determine vesting of MSUs. + References No definition available. + Details
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- Definition Unrecognized cost of unvested share-based compensation awards. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (i) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (i) -URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901 + Details
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- Definition The charge against earnings resulting from the aggregate write down of tangible assets from their carrying value to their fair value. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 205 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=6360339&loc=d3e1361-107760 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 360 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=6391110&loc=d3e2921-110230 + Details
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