Derivative Financial Instruments (Details 2) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Summary of gross asset balances of derivative instruments
Gross amounts of recognized assets	$ 4,660	$ 7,896
Gross amounts netted in the consolidated balance sheet	(4,294)	(7,704)
Net amounts of assets presented in the condensed consolidated balance sheet	366	192
Derivative Asset, Fair Value, Subject to Master Netting, Gross Asset Basis	(110)
Amounts subject to master netting arrangements presented on a gross basis		0
Counterparty A [Member] | Other Current Assets [Member]
Summary of gross asset balances of derivative instruments
Gross amounts of recognized assets	766	1,746
Gross amounts netted in the consolidated balance sheet	(766)	(1,746)
Net amounts of assets presented in the condensed consolidated balance sheet	0	0
Amounts subject to master netting arrangements presented on a gross basis	0
Counterparty A [Member] | Other Noncurrent Assets [Member]
Summary of gross asset balances of derivative instruments
Gross amounts of recognized assets	0	0
Gross amounts netted in the consolidated balance sheet	0	0
Net amounts of assets presented in the condensed consolidated balance sheet	0	0
Amounts subject to master netting arrangements presented on a gross basis	0
Counterparty B [Member]
Summary of gross asset balances of derivative instruments
Amounts subject to master netting arrangements presented on a gross basis	0
Counterparty B [Member] | Other Current Assets [Member]
Summary of gross asset balances of derivative instruments
Gross amounts of recognized assets	805	1,371
Gross amounts netted in the consolidated balance sheet	(805)	(1,371)
Net amounts of assets presented in the condensed consolidated balance sheet	0	0
Amounts subject to master netting arrangements presented on a gross basis	0
Counterparty B [Member] | Other Noncurrent Assets [Member]
Summary of gross asset balances of derivative instruments
Gross amounts of recognized assets	604	841
Gross amounts netted in the consolidated balance sheet	(353)	(668)
Net amounts of assets presented in the condensed consolidated balance sheet	251	173
Counterparty C [Member] | Other Current Assets [Member]
Summary of gross asset balances of derivative instruments
Gross amounts of recognized assets	1,789	2,886
Gross amounts netted in the consolidated balance sheet	(1,690)	(2,873)
Net amounts of assets presented in the condensed consolidated balance sheet	99	13
Derivative Asset, Fair Value, Subject to Master Netting, Gross Asset Basis	99
Counterparty C [Member] | Other Noncurrent Assets [Member]
Summary of gross asset balances of derivative instruments
Gross amounts of recognized assets	653	1,046
Gross amounts netted in the consolidated balance sheet	(637)	(1,046)
Net amounts of assets presented in the condensed consolidated balance sheet	16	0
Derivative Asset, Fair Value, Subject to Master Netting, Gross Asset Basis	11
Counterparty D [Member] | Other Current Assets [Member]
Summary of gross asset balances of derivative instruments
Gross amounts of recognized assets	43	6
Gross amounts netted in the consolidated balance sheet	(43)	0
Net amounts of assets presented in the condensed consolidated balance sheet	0	6
Derivative Asset, Fair Value, Subject to Master Netting, Gross Asset Basis	0
Counterparty D [Member] | Other Noncurrent Assets [Member]
Summary of gross asset balances of derivative instruments
Gross amounts of recognized assets	0	0
Gross amounts netted in the consolidated balance sheet	0	0
Net amounts of assets presented in the condensed consolidated balance sheet	0	0
Derivative Asset, Fair Value, Subject to Master Netting, Gross Asset Basis	$ 0