Consolidated Balance Sheets Balance Sheet Parenthetical $ in Thousands	Dec. 31, 2017 € / shares	Dec. 31, 2017 USD ($) shares	Dec. 31, 2016 € / shares	Dec. 31, 2016 USD ($) shares
Allowance for Doubtful Accounts Receivable, Current | $		$ 2,590		$ 3,139
Common Stock, Par or Stated Value Per Share | € / shares	€ 0.02		€ 0.02
Common Stock, Shares Authorized		200,000,000		200,000,000
Common Stock, Shares, Issued		44,796,252		44,796,252
Common Stock, Shares, Outstanding		44,184,205		44,151,261
Treasury Stock, Shares		612,047		644,991
Preferred Stock, Par or Stated Value Per Share | € / shares	€ 0.02		€ 0.02
Preferred Stock, Shares Authorized		6,000,000		6,000,000
Preferred Stock, Shares Issued		0		0
Preferred Stock, Shares Outstanding		0		0