Derivative Instruments (Details 2) - USD ($) $ in Thousands		9 Months Ended
		Sep. 30, 2015	Dec. 31, 2014
Derivative [Line Items]
Notional Amount		$ 117,900	$ 66,600
Fair Value		1,135	2,458
Bank of America, N.A. [Member]
Derivative [Line Items]
Notional Amount		17,000	8,700
Fair Value		6	439
Credit Suisse International [Member]
Derivative [Line Items]
Notional Amount		4,900	27,500
Fair Value		34	1,193
Societe Generale [Member]
Derivative [Line Items]
Notional Amount		75,100	25,400
Fair Value		611	756
Barclays Bank PLC [Member]
Derivative [Line Items]
Notional Amount		9,400	5,000
Fair Value		84	70
Citigroup Inc [Member]
Derivative [Line Items]
Notional Amount		11,500	0
Fair Value		$ 400	$ 0
Moody's [Member] | Bank of America, N.A. [Member]
Derivative [Line Items]
Credit Rating	[1]	A1
Moody's [Member] | Societe Generale [Member]
Derivative [Line Items]
Credit Rating	[1]	A2
Moody's [Member] | Barclays Bank PLC [Member]
Derivative [Line Items]
Credit Rating	[1]	A2
Moody's [Member] | Credit Suisse International [Member]
Derivative [Line Items]
Credit Rating	[1]	A1
Moody's [Member] | Citigroup Inc [Member]
Derivative [Line Items]
Credit Rating	[1]	Baa1
Standard & Poor's [Member] | Bank of America, N.A. [Member]
Derivative [Line Items]
Credit Rating	[1]	A
Standard & Poor's [Member] | Credit Suisse International [Member]
Derivative [Line Items]
Credit Rating	[1]	A
Standard & Poor's [Member] | Societe Generale [Member]
Derivative [Line Items]
Credit Rating	[1]	A
Standard & Poor's [Member] | Barclays Bank PLC [Member]
Derivative [Line Items]
Credit Rating	[1]	A-
Standard & Poor's [Member] | Citigroup Inc [Member]
Derivative [Line Items]
Credit Rating	[1]	A-

[1] As assigned by Standard & Poor’s Corporation (“S&P”) and Moody’s Investors Service, Inc. (“Moody’s”).