Derivative Financial Instruments (Details 2) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Offsetting Derivative Assets [Abstract]
Gross amounts of recognized assets	$ 7,896	$ 8,455
Gross amounts netted in the consolidated balance sheet	(7,704)	(3,306)
Net amounts of assets presented in the consolidated balance sheet	192	5,149
Amounts subject to master netting arrangements presented on a gross basis	0	82
Offsetting Derivative Liabilities [Abstract]
Gross amounts of recognized liabilities	10,649	3,976
Gross amounts netted in the consolidated balance sheet	(7,704)	(3,306)
Net amounts of liabilities presented in the consolidated balance sheet	2,945	670
Amounts subject to master netting arrangements presented on a gross basis	0	82
Counterparty A [Member] | Current Assets [Member]
Offsetting Derivative Assets [Abstract]
Gross amounts of recognized assets	1,746	6,445
Gross amounts netted in the consolidated balance sheet	(1,746)	(2,373)
Net amounts of assets presented in the consolidated balance sheet	0	4,072
Amounts subject to master netting arrangements presented on a gross basis	0	0
Offsetting Derivative Liabilities [Abstract]
Gross amounts of recognized liabilities		2,373
Gross amounts netted in the consolidated balance sheet		(2,373)
Net amounts of liabilities presented in the consolidated balance sheet		0
Amounts subject to master netting arrangements presented on a gross basis		0
Counterparty A [Member] | Other assets [Member]
Offsetting Derivative Assets [Abstract]
Gross amounts of recognized assets	0	1,096
Gross amounts netted in the consolidated balance sheet	0	(370)
Net amounts of assets presented in the consolidated balance sheet	0	726
Amounts subject to master netting arrangements presented on a gross basis	0	0
Offsetting Derivative Liabilities [Abstract]
Gross amounts of recognized liabilities		370
Gross amounts netted in the consolidated balance sheet		(370)
Net amounts of liabilities presented in the consolidated balance sheet		0
Amounts subject to master netting arrangements presented on a gross basis		0
Counterparty A [Member] | Current liabilities [Member]
Offsetting Derivative Liabilities [Abstract]
Gross amounts of recognized liabilities	2,550
Gross amounts netted in the consolidated balance sheet	(1,746)
Net amounts of liabilities presented in the consolidated balance sheet	804
Amounts subject to master netting arrangements presented on a gross basis	0
Counterparty A [Member] | Long-term liabilities [Member]
Offsetting Derivative Liabilities [Abstract]
Gross amounts of recognized liabilities	0
Gross amounts netted in the consolidated balance sheet	0
Net amounts of liabilities presented in the consolidated balance sheet	0
Amounts subject to master netting arrangements presented on a gross basis	0
Counterparty B [Member] | Current Assets [Member]
Offsetting Derivative Assets [Abstract]
Gross amounts of recognized assets	1,371	530
Gross amounts netted in the consolidated balance sheet	(1,371)	(224)
Net amounts of assets presented in the consolidated balance sheet	0	306
Amounts subject to master netting arrangements presented on a gross basis	0	82
Offsetting Derivative Liabilities [Abstract]
Gross amounts of recognized liabilities		894
Gross amounts netted in the consolidated balance sheet		(224)
Net amounts of liabilities presented in the consolidated balance sheet		670
Amounts subject to master netting arrangements presented on a gross basis		82
Counterparty B [Member] | Other assets [Member]
Offsetting Derivative Assets [Abstract]
Gross amounts of recognized assets	841	384
Gross amounts netted in the consolidated balance sheet	(668)	(339)
Net amounts of assets presented in the consolidated balance sheet	173	45
Amounts subject to master netting arrangements presented on a gross basis	0	0
Offsetting Derivative Liabilities [Abstract]
Gross amounts of recognized liabilities		339
Gross amounts netted in the consolidated balance sheet		(339)
Net amounts of liabilities presented in the consolidated balance sheet		0
Amounts subject to master netting arrangements presented on a gross basis		0
Counterparty B [Member] | Current liabilities [Member]
Offsetting Derivative Liabilities [Abstract]
Gross amounts of recognized liabilities	2,136
Gross amounts netted in the consolidated balance sheet	(1,371)
Net amounts of liabilities presented in the consolidated balance sheet	765
Amounts subject to master netting arrangements presented on a gross basis	0
Counterparty B [Member] | Long-term liabilities [Member]
Offsetting Derivative Liabilities [Abstract]
Gross amounts of recognized liabilities	668
Gross amounts netted in the consolidated balance sheet	(668)
Net amounts of liabilities presented in the consolidated balance sheet	0
Amounts subject to master netting arrangements presented on a gross basis	0
Counterparty C [Member] | Current Assets [Member]
Offsetting Derivative Assets [Abstract]
Gross amounts of recognized assets	2,886
Gross amounts netted in the consolidated balance sheet	(2,873)
Net amounts of assets presented in the consolidated balance sheet	13
Amounts subject to master netting arrangements presented on a gross basis	0
Counterparty C [Member] | Other assets [Member]
Offsetting Derivative Assets [Abstract]
Gross amounts of recognized assets	1,046
Gross amounts netted in the consolidated balance sheet	(1,046)
Net amounts of assets presented in the consolidated balance sheet	0
Amounts subject to master netting arrangements presented on a gross basis	0
Counterparty C [Member] | Current liabilities [Member]
Offsetting Derivative Liabilities [Abstract]
Gross amounts of recognized liabilities	3,996
Gross amounts netted in the consolidated balance sheet	(2,873)
Net amounts of liabilities presented in the consolidated balance sheet	1,123
Amounts subject to master netting arrangements presented on a gross basis	0
Counterparty C [Member] | Long-term liabilities [Member]
Offsetting Derivative Liabilities [Abstract]
Gross amounts of recognized liabilities	1,299
Gross amounts netted in the consolidated balance sheet	(1,046)
Net amounts of liabilities presented in the consolidated balance sheet	253
Amounts subject to master netting arrangements presented on a gross basis	0
Counterparty D [Member] | Current Assets [Member]
Offsetting Derivative Assets [Abstract]
Gross amounts of recognized assets	6
Gross amounts netted in the consolidated balance sheet	0
Net amounts of assets presented in the consolidated balance sheet	6
Amounts subject to master netting arrangements presented on a gross basis	0
Counterparty D [Member] | Other assets [Member]
Offsetting Derivative Assets [Abstract]
Gross amounts of recognized assets	0
Gross amounts netted in the consolidated balance sheet	0
Net amounts of assets presented in the consolidated balance sheet	0
Amounts subject to master netting arrangements presented on a gross basis	0
Counterparty D [Member] | Current liabilities [Member]
Offsetting Derivative Liabilities [Abstract]
Gross amounts of recognized liabilities	0
Gross amounts netted in the consolidated balance sheet	0
Net amounts of liabilities presented in the consolidated balance sheet	0
Amounts subject to master netting arrangements presented on a gross basis	0
Counterparty D [Member] | Long-term liabilities [Member]
Offsetting Derivative Liabilities [Abstract]
Gross amounts of recognized liabilities	0
Gross amounts netted in the consolidated balance sheet	0
Net amounts of liabilities presented in the consolidated balance sheet	0
Amounts subject to master netting arrangements presented on a gross basis	$ 0