Borrowing Arrangements - Long-Term Debt (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Long-term Debt
Total long-term debt	$ 225,000	$ 111,441
Less current portion of long-term debt	(5,000)	(7,500)
Long-term debt	220,000	103,941
U.S. credit agreement
Long-term Debt
Total long-term debt	$ 225,000	107,700
Japanese Term Loan due May 2017
Long-term Debt
Total long-term debt		$ 3,741