Financial Instruments Foreign currency forward contracts (Details) - Mar. 31, 2016 - Not Designated as Hedging Instrument - Forward Contracts	GBP (£)	SEK	AUD	EUR (€)	NZD	INR (₨)	NOK	USD ($)
NOK/EUR | Currency Purchased Forward
Derivative [Line Items]
Outstanding foreign currency forward contract | NOK							NOK 44,100,000
NOK/EUR | Currency Sold Forward
Derivative [Line Items]
Outstanding foreign currency forward contract				€ 4,682,175
USD/EUR | Currency Purchased Forward
Derivative [Line Items]
Outstanding foreign currency forward contract | $								$ 11,200,000
USD/EUR | Currency Sold Forward
Derivative [Line Items]
Outstanding foreign currency forward contract				9,829,994
EUR/GBP | Currency Purchased Forward
Derivative [Line Items]
Outstanding foreign currency forward contract				7,000,000
EUR/GBP | Currency Sold Forward
Derivative [Line Items]
Outstanding foreign currency forward contract | £	£ 5,553,870
AUD/EUR | Currency Purchased Forward
Derivative [Line Items]
Outstanding foreign currency forward contract | AUD			AUD 2,950,000
AUD/EUR | Currency Sold Forward
Derivative [Line Items]
Outstanding foreign currency forward contract				1,983,327
EUR/SEK | Currency Purchased Forward
Derivative [Line Items]
Outstanding foreign currency forward contract				1,300,000
EUR/SEK | Currency Sold Forward
Derivative [Line Items]
Outstanding foreign currency forward contract | SEK		SEK 12,003,290
AUD/NZD | Currency Purchased Forward
Derivative [Line Items]
Outstanding foreign currency forward contract | AUD			AUD 360,432
AUD/NZD | Currency Sold Forward
Derivative [Line Items]
Outstanding foreign currency forward contract | NZD					NZD 400,000
INR/USD | Currency Purchased Forward
Derivative [Line Items]
Outstanding foreign currency forward contract | ₨						₨ 507,282,975
INR/USD | Currency Sold Forward
Derivative [Line Items]
Outstanding foreign currency forward contract | $								7,650,000
INR/EUR | Currency Purchased Forward
Derivative [Line Items]
Outstanding foreign currency forward contract | ₨						₨ 233,478,980
INR/EUR | Currency Sold Forward
Derivative [Line Items]
Outstanding foreign currency forward contract				€ 3,100,000
USD/GBP | Currency Purchased Forward
Derivative [Line Items]
Outstanding foreign currency forward contract | $								$ 1,000,000
USD/GBP | Currency Sold Forward
Derivative [Line Items]
Outstanding foreign currency forward contract | £	£ 695,410