Note 12 - Debt Obligations (Details) - Convertible Debt Interest Expense (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Note 12 - Debt Obligations (Details) - Convertible Debt Interest Expense [Line Items]
Amortization of debt discount expense	$ 8,273	$ 9,375	$ 9,833
Amortization of debt issue costs	1,372us-gaap_AmortizationOfFinancingCosts	2,365us-gaap_AmortizationOfFinancingCosts	3,135us-gaap_AmortizationOfFinancingCosts
Convertible Notes 2017 [Member]
Note 12 - Debt Obligations (Details) - Convertible Debt Interest Expense [Line Items]
Interest expense related to the contractual interest coupon	13,755	3,258
Amortization of debt discount expense	4,005	959
Amortization of debt issue costs	610	135
Interest expense related to the Convertible Notes	18,370	4,352
Convertible Notes 2015 [Member]
Note 12 - Debt Obligations (Details) - Convertible Debt Interest Expense [Line Items]
Interest expense related to the contractual interest coupon	4,386	9,622	11,111
Amortization of debt discount expense	2,896	6,051	6,698
Amortization of debt issue costs	762	977	956
Interest expense related to the Convertible Notes	$ 8,044	$ 16,650	$ 18,765

Name:	bpz_Note12DebtObligationsDetailsConvertibleDebtInterestExpenseLineItems
Namespace Prefix:	bpz_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Amount of noncash expense included in interest expense to issue debt and obtain financing associated with the related debt instruments. Alternate captions include noncash interest expense.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 28

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 225

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SX 210.5-03.8)

-URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 8

-Article 5

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Paragraph 8

-Article 9

+ Details

Name:	us-gaap_AmortizationOfFinancingCosts
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of noncash expense included in interest expense to allocate debt discount and premium, and the costs to issue debt and obtain financing over the related debt instruments. Alternate captions include noncash interest expense.

+ References

+ Details

Name:	us-gaap_AmortizationOfFinancingCostsAndDiscounts
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of the cost of borrowed funds accounted for as interest expense for debt.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 225

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SX 210.5-03.8)

-URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 8

-Article 5

+ Details

Name:	us-gaap_InterestExpenseDebt
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Represents the portion of interest incurred in the period on debt arrangements that was charged against earnings, excluding amortization of debt discount (premium) and financing costs.

+ References

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 8

-Article 5

+ Details

Name:	us-gaap_InterestExpenseDebtExcludingAmortization
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

Name:	us-gaap_DebtInstrumentAxis=bpz_ConvertibleNotes2015Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=bpz_ConvertibleNotes2017Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: