Offsetting (Details) - USD ($) $ in Thousands		Mar. 31, 2016	Dec. 31, 2015
Offsetting [Abstract]
Gross amounts of recognized, asset	[1]	$ 36,747	$ 33,159
Gross amount offset in the balance sheet		0	0
Net amounts of asset/ liabilities presented in the balance sheet, asset		36,747	33,159
Gross amounts not offset in the balance sheet, financial instruments, asset		(2,405)	(1,037)
Gross amounts not offset in the balance sheet, cash collateral received/ pledged		(12,335)	(10,222)
Net amount, asset		22,007	21,900
Gross amounts of recognized, liability	[1]	(39,808)	(47,916)
Gross amount offset in the balance sheet		0	0
Net amounts presented in the balance sheet, liability		(39,808)	(47,916)
Gross amounts not offset in the balance sheet, financial instruments, liability		2,405	1,037
Gross amounts not offset in the balance sheet, cash collateral received		7,076	25,904
Net amount, liability		$ (30,327)	$ (20,975)

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