Financing Arrangements (Tables)

6 Months Ended

Jun. 30, 2017

Debt Instrument [Line Items]

Schedule of Convertible Debt Interest Expense [Table Text Block]

During the three and six months endedJune 30, 2017, the Company recognized interest cost on the Notes as follows (in thousands):

	Three Months Ended June 30, 2017		Six Months Ended June 30, 2017		Three and Six Months Ended June 30, 2016
Contractual interest cost based on 3.25% of the principal amount per annum	$	2,032	$	4,064	$	2,031
Amortization of debt discount	2,655		5,242		2,396
Total interest cost	$	4,687	$	9,306	$	4,427

Convertible Debt [Table Text Block]

The carrying amount of the Notes consisted of the following (in thousands):

	June 30, 2017			December 31, 2016
Liability component:
Principal amount	$	250,000		$	250,000
Less: debt discount	(65,763		)	(71,005		)
Net carrying amount of liability component	$	184,237		$	178,995
Net carrying amount of equity component	$	67,014		$	67,014