Debt and Credit Facilities Debt and Credit Facilities (Schedule of Convertible Debt Interest Expense) (Details) - Convertible Senior Notes due 2022 - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2017
Debt Instrument [Line Items]
Coupon interest expense	$ 37	$ 37
Amortization of debt discount - equity component	18	18
Amortization of debt discount - initial purchaser	5	5
Amortization of transaction costs	1	1
Total interest expense	$ 61	$ 61