Other (Expense) Income (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Other Income and Expenses [Abstract]
Foreign Currency Transaction Gain (Loss), before Tax	$ (7,913)	$ (3,958)	$ (3,379)
Secondary Offering Underwriting Fees	0	(5,900)	0
Gain (Loss) on Sale of Accounts Receivable	(931)	(801)	(1,017)
Miscellaneous Income Expense	1,711	0	(44)
Gain on remeasurement of previously held equity interest	0	0	14,199
Other Nonoperating Income (Expense)	$ (7,133)	$ (10,659)	$ 9,759