Earnings per share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Numerator:
Net income (loss)	$ 3,991	$ (21,520)
Interest expense applicable to convertible debt, net of tax	716	0
Amortization of debt issuance costs, net of tax	215	0
Adjusted net income (loss)	$ 4,922	$ (21,520)
Denominator:
Weighted-average number of shares-basic (in shares)	39,542,656	37,949,358
Dilutive securities-equity awards (in shares)	1,096,711	0
Incremental Common Shares Attributable to Dilutive Effect of Conversion of Debt Securities	7,720,525	0
Weighted-average number of shares-diluted (in shares)	48,359,892	37,949,358
Net income (loss) per share - basic	$ 0.10	$ (0.57)
Adjusted net (loss) income per share-diluted	$ 0.10	$ (0.57)
Stock Options [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive shares excluded from calculation (in shares)		5,100,000
Convertible debt [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive shares excluded from calculation (in shares)		7,700,000