Offsetting (Details) - USD ($) $ in Thousands		Sep. 30, 2015	Dec. 31, 2014
Offsetting [Abstract]
Gross amounts of recognized, asset	[1]	$ 25,049	$ 21,521
Gross amount offset in the balance sheet		0	0
Net amounts of asset/ liabilities presented in the balance sheet, asset		25,049	21,521
Gross amounts not offset in the balance sheet, financial instruments, asset		(520)	(766)
Gross amounts not offset in the balance sheet, cash collateral received/ pledged		(9,440)	(8,536)
Net amount, asset		15,089	12,219
Gross amounts of recognized, liability	[1]	(52,062)	(27,977)
Gross amount offset in the balance sheet		0	0
Net amounts presented in the balance sheet, liability		(52,062)	(27,977)
Gross amounts not offset in the balance sheet, financial instruments, liability		520	766
Gross amounts not offset in the balance sheet, cash collateral received		47,430	14,858
Net amount, liability		$ (4,112)	$ (12,353)

[1] Amounts include all derivative instruments, irrespective of whether there is a legally enforceable master netting arrangement in place.