Derivative Financial Instruments (Details 2) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Summary of gross asset balances of derivative instruments
Gross amounts of recognized assets	$ 9,216	$ 7,896
Gross amounts netted in the consolidated balance sheet	(4,009)	(7,704)
Net amounts of assets presented in the condensed consolidated balance sheet	5,207	192
Derivative Asset, Fair Value, Subject to Master Netting, Gross Asset Basis	0	0
Counterparty A [Member] | Other Current Assets [Member]
Summary of gross asset balances of derivative instruments
Gross amounts of recognized assets	1,425	1,746
Gross amounts netted in the consolidated balance sheet	(534)	(1,746)
Net amounts of assets presented in the condensed consolidated balance sheet	891	0
Derivative Asset, Fair Value, Subject to Master Netting, Gross Asset Basis	0	0
Counterparty A [Member] | Other Noncurrent Assets [Member]
Summary of gross asset balances of derivative instruments
Gross amounts of recognized assets	568	0
Gross amounts netted in the consolidated balance sheet	(243)	0
Net amounts of assets presented in the condensed consolidated balance sheet	325	0
Derivative Asset, Fair Value, Subject to Master Netting, Gross Asset Basis	0	0
Counterparty B [Member] | Other Current Assets [Member]
Summary of gross asset balances of derivative instruments
Gross amounts of recognized assets	1,369	1,371
Gross amounts netted in the consolidated balance sheet	(556)	(1,371)
Net amounts of assets presented in the condensed consolidated balance sheet	813	0
Derivative Asset, Fair Value, Subject to Master Netting, Gross Asset Basis	0	0
Counterparty B [Member] | Other Noncurrent Assets [Member]
Summary of gross asset balances of derivative instruments
Gross amounts of recognized assets	461	841
Gross amounts netted in the consolidated balance sheet	(233)	(668)
Net amounts of assets presented in the condensed consolidated balance sheet	228	173
Derivative Asset, Fair Value, Subject to Master Netting, Gross Asset Basis	0	0
Counterparty C [Member] | Other Current Assets [Member]
Summary of gross asset balances of derivative instruments
Gross amounts of recognized assets	2,991	2,886
Gross amounts netted in the consolidated balance sheet	(1,568)	(2,873)
Net amounts of assets presented in the condensed consolidated balance sheet	1,423	13
Derivative Asset, Fair Value, Subject to Master Netting, Gross Asset Basis	0	0
Counterparty C [Member] | Other Noncurrent Assets [Member]
Summary of gross asset balances of derivative instruments
Gross amounts of recognized assets	1,060	1,046
Gross amounts netted in the consolidated balance sheet	(620)	(1,046)
Net amounts of assets presented in the condensed consolidated balance sheet	440	0
Derivative Asset, Fair Value, Subject to Master Netting, Gross Asset Basis	0	0
Counterparty D [Member] | Other Current Assets [Member]
Summary of gross asset balances of derivative instruments
Gross amounts of recognized assets	9	6
Gross amounts netted in the consolidated balance sheet	(8)	0
Net amounts of assets presented in the condensed consolidated balance sheet	1	6
Derivative Asset, Fair Value, Subject to Master Netting, Gross Asset Basis	0	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	0
Counterparty E [Member] | Other Current Assets [Member]
Summary of gross asset balances of derivative instruments
Gross amounts of recognized assets	966
Gross amounts netted in the consolidated balance sheet	(165)
Net amounts of assets presented in the condensed consolidated balance sheet	801
Derivative Asset, Fair Value, Subject to Master Netting, Gross Asset Basis	0
Counterparty E [Member] | Other Noncurrent Assets [Member]
Summary of gross asset balances of derivative instruments
Gross amounts of recognized assets	367
Gross amounts netted in the consolidated balance sheet	(82)
Net amounts of assets presented in the condensed consolidated balance sheet	285
Derivative Asset, Fair Value, Subject to Master Netting, Gross Asset Basis	$ 0