Financial Instruments Foreign currency forward contracts (Details) - Sep. 30, 2015 - Not Designated as Hedging Instrument - Forward Contracts	GBP (£)	SEK	AUD	EUR (€)	INR (₨)	NOK	USD ($)
EUR/NOK | Currency Purchased Forward
Derivative [Line Items]
Outstanding foreign currency forward contract | NOK						NOK 25,600,000
EUR/NOK | Currency Sold Forward
Derivative [Line Items]
Outstanding foreign currency forward contract				€ 2,690,263
EUR/USD 1 | Currency Purchased Forward
Derivative [Line Items]
Outstanding foreign currency forward contract | $							$ 17,700,000
EUR/USD 1 | Currency Sold Forward
Derivative [Line Items]
Outstanding foreign currency forward contract				15,864,764
USD/GPB | Currency Purchased Forward
Derivative [Line Items]
Outstanding foreign currency forward contract | $							2,200,000
USD/GPB | Currency Sold Forward
Derivative [Line Items]
Outstanding foreign currency forward contract | £	£ 1,456,857
EUR/GBP | Currency Purchased Forward
Derivative [Line Items]
Outstanding foreign currency forward contract				5,750,000
EUR/GBP | Currency Sold Forward
Derivative [Line Items]
Outstanding foreign currency forward contract | £	£ 4,253,793
EUR/AUD | Currency Purchased Forward
Derivative [Line Items]
Outstanding foreign currency forward contract | AUD			AUD 2,900,000
EUR/AUD | Currency Sold Forward
Derivative [Line Items]
Outstanding foreign currency forward contract				1,822,180
SEK/EUR | Currency Purchased Forward
Derivative [Line Items]
Outstanding foreign currency forward contract				1,900,000
SEK/EUR | Currency Sold Forward
Derivative [Line Items]
Outstanding foreign currency forward contract | SEK		SEK 17,765,950
USD/INR | Currency Purchased Forward
Derivative [Line Items]
Outstanding foreign currency forward contract | ₨					₨ 494,936,328
USD/INR | Currency Sold Forward
Derivative [Line Items]
Outstanding foreign currency forward contract | $							$ 7,440,000
EUR/INR | Currency Purchased Forward
Derivative [Line Items]
Outstanding foreign currency forward contract | ₨					₨ 119,670,720
EUR/INR | Currency Sold Forward
Derivative [Line Items]
Outstanding foreign currency forward contract				€ 1,600,000