Commitments and contingencies	6 Months Ended
Jun. 30, 2015
Commitments And Contingencies Disclosure [Abstract]
Commitments and contingencies	6. Commitments and contingencies The Company is party to various agreements, principally relating to licensed technology, that require future payments relating to milestones not met at June 30, 2015 and December 31, 2014 or royalties on future sales of specified products. The Company enters into standard indemnification agreements in the ordinary course of business. Pursuant to these agreements, the Company indemnifies, holds harmless, and agrees to reimburse the indemnified party for losses suffered or incurred by the indemnified party, generally the Company’s business partners or customers, in connection with claims by any third party with respect to the Company’s products or business activities. The term of these indemnification agreements is generally perpetual any time after execution of the agreement. The maximum potential amount of future payments the Company could be required to make under these indemnification agreements is unlimited. The Company has never incurred costs to defend lawsuits or settle claims related to these indemnification agreements. The Company’s wholly-owned subsidiary bluebird bio France – SARL participates in the French Crédit d’Impôt Recherche (“CIR”) program, which allows companies to monetize up to 30% of eligible research expenses. The Company received aggregate reimbursement of €1.1 million related to years 2011 through 2013. The Company applied for €0.7 million related to 2014, which was classified in current assets within the condensed consolidated balance sheets as of June 30, 2015 and was received during the third quarter of 2015. The Company has not yet applied for €0.3 million related to the six months ended June 30, 2015, which is classified as non-current assets within the condensed consolidated balance sheets as of June 30, 2015. The years 2011 through 2015 are open and subject to examination. On June 30, 2014, the Company acquired Pregenen. During the second quarter of 2015, a $1.0 million milestone under the Stock Purchase Agreement was achieved, which resulted in a $1.0 million payment to the former equityholders of Pregenen during the third quarter of 2015. The Company may be required to make up to an additional $134.0 million in future contingent cash payments to the former equityholders of Pregenen upon the achievement of certain preclinical, clinical and commercial milestones related to the Pregenen technology, of which $14.0 million relates to preclinical milestones, $20.1 million relates to clinical milestones and $99.9 million relates to commercial milestones. In accordance with accounting for business combinations guidance, contingent consideration liabilities are required to be recognized on the condensed consolidated balance sheets at fair value. Estimating the fair value of contingent consideration requires the use of significant assumptions primarily relating to probabilities of successful achievement of certain preclinical, clinical and commercial milestones, the expected timing in which these milestones will be achieved and discount rates. The use of different assumptions could result in materially different estimates of fair value. See Note 4, “Fair value measurements,” for additional information. On June 29, 2015, the Company entered into a lease agreement for additional office space located at 215 First Street, Cambridge, Massachusetts. Under the terms of the lease, the Company leased approximately 15,120 square feet starting on July 13, 2015 for $483,840 per year in base rent, which is subject to a 3% annual increase plus certain operating expenses and taxes. The lease will continue until the end of the sixtieth full calendar month following the date the landlord delivers the premises to the Company. Under the terms of the lease, the Company will also lease an additional 8,075 square feet of office space in the same premises starting on January 1, 2016 for an additional $258,400 per year in base rent, which is subject to a 3% annual increase plus certain operating expenses and taxes.

6. Commitments and contingencies

The Company is party to various agreements, principally relating to licensed technology, that require future payments relating to milestones not met at June 30, 2015 and December 31, 2014 or royalties on future sales of specified products.

The Company enters into standard indemnification agreements in the ordinary course of business. Pursuant to these agreements, the Company indemnifies, holds harmless, and agrees to reimburse the indemnified party for losses suffered or incurred by the indemnified party, generally the Company’s business partners or customers, in connection with claims by any third party with respect to the Company’s products or business activities. The term of these indemnification agreements is generally perpetual any time after execution of the agreement. The maximum potential amount of future payments the Company could be required to make under these indemnification agreements is unlimited. The Company has never incurred costs to defend lawsuits or settle claims related to these indemnification agreements.

The Company’s wholly-owned subsidiary bluebird bio France – SARL participates in the French Crédit d’Impôt Recherche (“CIR”) program, which allows companies to monetize up to 30% of eligible research expenses. The Company received aggregate reimbursement of €1.1 million related to years 2011 through 2013. The Company applied for €0.7 million related to 2014, which was classified in current assets within the condensed consolidated balance sheets as of June 30, 2015 and was received during the third quarter of 2015. The Company has not yet applied for €0.3 million related to the six months ended June 30, 2015, which is classified as non-current assets within the condensed consolidated balance sheets as of June 30, 2015. The years 2011 through 2015 are open and subject to examination.

On June 30, 2014, the Company acquired Pregenen. During the second quarter of 2015, a $1.0 million milestone under the Stock Purchase Agreement was achieved, which resulted in a $1.0 million payment to the former equityholders of Pregenen during the third quarter of 2015. The Company may be required to make up to an additional $134.0 million in future contingent cash payments to the former equityholders of Pregenen upon the achievement of certain preclinical, clinical and commercial milestones related to the Pregenen technology, of which $14.0 million relates to preclinical milestones, $20.1 million relates to clinical milestones and $99.9 million relates to commercial milestones. In accordance with accounting for business combinations guidance, contingent consideration liabilities are required to be recognized on the condensed consolidated balance sheets at fair value. Estimating the fair value of contingent consideration requires the use of significant assumptions primarily relating to probabilities of successful achievement of certain preclinical, clinical and commercial milestones, the expected timing in which these milestones will be achieved and discount rates. The use of different assumptions could result in materially different estimates of fair value. See Note 4, “Fair value measurements,” for additional information.

On June 29, 2015, the Company entered into a lease agreement for additional office space located at 215 First Street, Cambridge, Massachusetts. Under the terms of the lease, the Company leased approximately 15,120 square feet starting on July 13, 2015 for $483,840 per year in base rent, which is subject to a 3% annual increase plus certain operating expenses and taxes. The lease will continue until the end of the sixtieth full calendar month following the date the landlord delivers the premises to the Company. Under the terms of the lease, the Company will also lease an additional 8,075 square feet of office space in the same premises starting on January 1, 2016 for an additional $258,400 per year in base rent, which is subject to a 3% annual increase plus certain operating expenses and taxes.