Borrowing Arrangements - Long-Term Debt (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Long-term Debt
Total long-term debt	$ 246,367	$ 225,000
Less current portion of long-term debt	(5,000)	(5,000)
Long-term debt	241,367	220,000
U.S. Credit Agreement
Long-term Debt
Total long-term debt	244,140	$ 225,000
Japanese Credit Agreement
Long-term Debt
Total long-term debt	$ 2,227