Derivatives - Forward Notional Contracts (Details) - Sep. 30, 2018 - Foreign currency forward contracts € in Thousands, ₩ in Thousands, ¥ in Thousands, ¥ in Thousands, £ in Thousands, kr in Thousands, kr in Thousands, SFr in Thousands, R$ in Thousands, $ in Thousands, $ in Thousands, $ in Thousands, $ in Thousands, $ in Thousands	SGD ($)	EUR (€)	SEK (kr)	GBP (£)	KRW (₩)	JPY (¥)	AUD ($)	CNY (¥)	DKK (kr)	HKD ($)	CAD ($)	MXN ($)	BRL (R$)	CHF (SFr)
Designated as hedging instrument | Derivatives designated as cash flow hedges
Derivative [Line Items]
Notional amount of derivative		€ 12,270	kr 12,780	£ 3,355		¥ 330,000		¥ 60,000	kr 10,835		$ 2,460	$ 93,575		SFr 1,215
Not designated as hedging instrument
Derivative [Line Items]
Notional amount of derivative	$ 6,900	€ 25,861	kr 10,536	£ 1,584	₩ 2,700,000	¥ 260,000	$ 11,150	¥ 95,228	kr 2,885	$ 11,000	$ 3,098	$ 18,700	R$ 8,500	SFr 255