ESPP contributions by Employees

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- Definition

Inducement grants - Feb 2014

+ References

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- Definition

Maximum Amount Contributable By Employees Under ESPP- Annually

+ References

No definition available.

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- Definition

Maximum Amount Contributable by employees under ESPP- Half yearly

+ References

No definition available.

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- Definition

Share-based compensation arrangement by share-based payment, Minimum Employee Subscription rate

+ References

No definition available.

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- Definition

Maximum number of shares issuable upon vesting of MSUs initially granted.

+ References

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- Definition

Stock Price at Year End

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No definition available.

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- Definition

Total shareholder return period used to determine vesting of MSUs.

+ References

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- Definition

Discount rate from fair value on offering date that participants pay for shares.

+ References

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- Definition

The highest percentage of annual salary that an employee is permitted to utilize with respect to the plan.

+ References

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- Definition

Number of equity instruments other than options outstanding, including both vested and non-vested instruments.

+ 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 (c)(1)(i)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

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- Definition

Number of additional shares authorized for issuance under an established share-based compensation plan.

+ References

No definition available.

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- Definition

The maximum number of shares (or other type of equity) originally approved (usually by shareholders and board of directors), net of any subsequent amendments and adjustments, for awards under the equity-based compensation plan. As stock or unit options and equity instruments other than options are awarded to participants, the shares or units remain authorized and become reserved for issuance under outstanding awards (not necessarily vested).

+ References

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- Definition

Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares.

+ References

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- Definition

Number of options outstanding, including both vested and non-vested options.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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- Definition

Number of shares issued during the period as a result of an employee stock purchase plan.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Article 3

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 505

-SubTopic 10

-Section 50

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-Name Accounting Standards Codification

-Topic 505

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-Section S99

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-Subparagraph (SX 210.3-04)

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-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 29, 30

-Article 5

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Noncash Share-based Compensation Narrative (Details) (USD $)	1 Months Ended		12 Months Ended
	Feb. 28, 2014	Feb. 29, 2012	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation arrangement by share-based payment, Minimum Employee Subscription rate			1.00%
Inducement grants - Feb 2014	308,250pro_InducementgrantsFeb2014
Share-based Compensation Arrangement by Share-based Payment Award, Number of Additional Shares Authorized		900,000
Total shareholder return period for vesting of MSUs			three
Stock Price at Year End			$ 27.48pro_StockPriceAtYearEnd
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Total Intrinsic Value			$ 4,500,000	$ 5,200,000	$ 600,000
Shares issuable upon vesting of MSUs, maximum			200.00%
Share-based Compensation Arrangement by Share-based Payment Award, Maximum Employee Subscription Rate			10.00%
Share-based Compensation Arrangement by Share-based Payment Award, Discount from Market Price, Offering Date			5.00%
Maximum Amount Contributable by employees under ESPP- Half yearly			5,000
Maximum Amount Contributable By Employees Under ESPP- Annually			10,000
Stock Issued During Period, Shares, Employee Stock Purchase Plans			13,392
ESPP contributions by Employees			$ 400,000pro_ESPPcontributionsbyEmployees
Market Share Units (MSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Inducement grants - Feb 2014	75,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number			444,000	469,000
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding, Number			444,272	469,000
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Inducement grants - Feb 2014	233,250
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding, Number			1,830,291	1,543,000
Employee Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized			486,608
2007 Equity Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized			8,168,000
2007 Equity Incentive Plan [Member] \| Market Share Units (MSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding, Number			369,272
2007 Equity Incentive Plan [Member] \| Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding, Number			1,631,041
December 2013 Market Stock Unit Performance Award [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total shareholder return period for vesting of MSUs			two
2007 Equity Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number			3,634,758