Financing Arrangements (Details) - Expenses in Relation to Convertible Notes - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Debt Instrument [Line Items]
Deferred financing cost amortization	$ 10,791	$ 4,283	$ 9,985
Convertible Debt [Member]
Debt Instrument [Line Items]
Interest expense at 3.50% coupon rate	687	2,205	4,105
Debt discount amortization	750	2,421	4,317
Deferred financing cost amortization	136	438	780
Loss on conversion	0	1,235	990
Interest expense	$ 1,573	$ 6,299	$ 10,192
Coupon Rate	3.50%
Debt Instrument, Redemption, Period One [Member] | Convertible Debt [Member]
Debt Instrument [Line Items]
Debt Instrument, Convertible, Conversion Penalty Percentage	0.50%
Debt Instrument, Redemption, Period Two [Member] | Convertible Debt [Member]
Debt Instrument [Line Items]
Debt Instrument, Convertible, Conversion Penalty Percentage	0.25%