Earnings per share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2017		Jun. 30, 2016		Jun. 30, 2017	Jun. 30, 2016
Numerator [Abstract]
Net Income (loss) from continuing operations	$ 4,616		$ (2,042)		$ 15,101	$ 9,847
Interest expense, net of tax	835		0		1,742	1,302
Amortization of debt issuance costs, net of tax	195		0		391	391
Net income (loss), adjusted from continuing operations	5,646		(2,042)		17,234	11,540
Net Loss from discontinued operations	0		(8,905)		0	(16,803)
Net income (loss), adjusted	$ 5,646		$ (10,947)		$ 17,234	$ (5,263)
Denominator [Abstract]
Weighted-average number of shares-basic (in shares)	41,013,764		40,202,821		40,871,540	39,872,738
Dilutive securities-equity awards (in shares)	968,354		0		931,263	1,191,076
Dilutive securities-convertible debt	8,096,476		0		8,096,488	7,720,525
Weighted-average number of shares-diluted (in shares)	50,078,594		40,202,821		49,899,291	48,784,339
Net income (loss) per share from continuing operations-basic (in dollars per share)	$ 0.11		$ (0.05)		$ 0.37	$ 0.25
Net loss per share from discontinued operations-basic (in dollars per share)	0		(0.22)		0	(0.42)
Net income (loss) per share - basic (in dollars per share)	0.11		(0.27)		0.37	(0.17)
Net income (loss) from continuing operations - diluted (in dollars per share)	0.11	[1]	(0.05)	[1]	0.35	0.24
Net loss per share from discontinued operations-diluted (in dollars per share)	0		(0.22)		0	(0.34)
Net income (loss) per share - diluted (in dollars per share)	$ 0.11	[1]	$ (0.27)	[1]	$ 0.35	$ (0.10)
Stock Options [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive shares excluded from calculation (in shares)	400,000		3,600,000		400,000
Convertible debt [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive shares excluded from calculation (in shares)			7,700,000

[1] See "Earnings per share" for details on calculation.