Debt and Credit Facilities (Schedule of Convertible Debt Interest Expense) (Details) - Convertible Senior Notes due 2022 - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Coupon interest expense	$ 2,530	$ 661
Amortization of debt discount - equity component	1,366	330
Amortization of debt discount - initial purchaser	407	98
Amortization of transaction costs	64	16
Total interest expense	$ 4,367	$ 1,105