Fair Value Measurements - Assets and liabilities at fair value (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Liabilities
Fair value asset, Transfer between Level 1 to Level 2	$ 0
Fair value asset, Transfer between Level 2 to Level 1	0
Fair value Liabilities, Transfer between Level 1 to Level 2	0
Fair value Liabilities, Transfer between Level 2 to Level 1	0
Level 1
Assets
Total assets	14,088	$ 16,682
Liabilities
Total liabilities	1,846	2,129
Level 2
Assets
Total assets	16,643	14,614
Liabilities
Total liabilities	1,138	1,596
Level 3
Liabilities
Total liabilities		22,884
Other current assets | Rabbi trust | Level 1
Assets
Total assets	6,994	13,111
Other current assets | Foreign exchange derivative instruments | Level 2
Assets
Total assets	11,357	13,824
Other noncurrent assets | Rabbi trust | Level 1
Assets
Total assets	5,248	1,442
Other noncurrent assets | Foreign exchange derivative instruments | Level 2
Assets
Total assets	5,286	790
Other noncurrent assets | Deferred compensation program assets | Level 1
Assets
Total assets	1,846	2,129
Other current liabilities | Foreign exchange derivative instruments | Level 2
Liabilities
Total liabilities	1,106	1,265
Other current liabilities | Common stock warrants | Level 3
Liabilities
Total liabilities		22,884
Other noncurrent liabilities | Foreign exchange derivative instruments | Level 2
Liabilities
Total liabilities	32	331
Other noncurrent liabilities | Deferred compensation program liabilities | Level 1
Liabilities
Total liabilities	$ 1,846	$ 2,129