Fair Value Measurements - Financial assets and financial liabilities (Details) (Fair value measurements, recurring, USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Fair Value
Fair Value Assets and Liabilities Measured On Recurring Basis [Line Items]
Asset for foreign currency derivative financial instruments (including forward contracts)	$ 3
Liability for foreign currency derivative financial instruments (including forward contracts)		(1)
Quoted Prices in Active Markets for Identical Items (Level 1)
Fair Value Assets and Liabilities Measured On Recurring Basis [Line Items]
Asset for foreign currency derivative financial instruments (including forward contracts)
Liability for foreign currency derivative financial instruments (including forward contracts)
Significant Other Observable Inputs (Level 2)
Fair Value Assets and Liabilities Measured On Recurring Basis [Line Items]
Asset for foreign currency derivative financial instruments (including forward contracts)	3
Liability for foreign currency derivative financial instruments (including forward contracts)		(1)
Significant Unobservable Inputs (Level 3)
Fair Value Assets and Liabilities Measured On Recurring Basis [Line Items]
Asset for foreign currency derivative financial instruments (including forward contracts)
Liability for foreign currency derivative financial instruments (including forward contracts)