Derivative Financial Instruments (Details 3) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Summary of gross liability balances of derivative instruments
Gross amounts of recognized liabilities	$ 15,155	$ 10,649
Gross amounts netted in the consolidated balance sheet	(3,866)	(7,704)
Net amounts of liabilities presented in the condensed consolidated balance sheet	11,289	2,945
Derivative Asset, Fair Value, Subject to Master Netting, Gross Asset Basis	(83)	0
Counterparty A [Member] | Other Current Liabilities [Member]
Summary of gross liability balances of derivative instruments
Gross amounts of recognized liabilities	3,078	2,550
Gross amounts netted in the consolidated balance sheet	(200)	(1,746)
Net amounts of liabilities presented in the condensed consolidated balance sheet	2,878	804
Derivative Asset, Fair Value, Subject to Master Netting, Gross Asset Basis	0	0
Counterparty A [Member] | Other Noncurrent Liabilities [Member]
Summary of gross liability balances of derivative instruments
Gross amounts of recognized liabilities	473	0
Gross amounts netted in the consolidated balance sheet	(306)	0
Net amounts of liabilities presented in the condensed consolidated balance sheet	167	0
Derivative Asset, Fair Value, Subject to Master Netting, Gross Asset Basis	0	0
Counterparty B [Member]
Summary of gross liability balances of derivative instruments
Derivative Asset, Fair Value, Subject to Master Netting, Gross Asset Basis	(83)
Counterparty B [Member] | Other Current Liabilities [Member]
Summary of gross liability balances of derivative instruments
Gross amounts of recognized liabilities	2,761	2,136
Gross amounts netted in the consolidated balance sheet	(482)	(1,371)
Net amounts of liabilities presented in the condensed consolidated balance sheet	2,279	765
Derivative Asset, Fair Value, Subject to Master Netting, Gross Asset Basis		0
Counterparty B [Member] | Other Noncurrent Liabilities [Member]
Summary of gross liability balances of derivative instruments
Gross amounts of recognized liabilities	692	668
Gross amounts netted in the consolidated balance sheet	(468)	(668)
Net amounts of liabilities presented in the condensed consolidated balance sheet	224	0
Derivative Asset, Fair Value, Subject to Master Netting, Gross Asset Basis	0	0
Counterparty C [Member] | Other Current Liabilities [Member]
Summary of gross liability balances of derivative instruments
Gross amounts of recognized liabilities	5,738	3,996
Gross amounts netted in the consolidated balance sheet	(946)	(2,873)
Net amounts of liabilities presented in the condensed consolidated balance sheet	4,792	1,123
Derivative Asset, Fair Value, Subject to Master Netting, Gross Asset Basis	0	0
Counterparty C [Member] | Other Noncurrent Liabilities [Member]
Summary of gross liability balances of derivative instruments
Gross amounts of recognized liabilities	1,523	1,299
Gross amounts netted in the consolidated balance sheet	(889)	(1,046)
Net amounts of liabilities presented in the condensed consolidated balance sheet	634	253
Derivative Asset, Fair Value, Subject to Master Netting, Gross Asset Basis	0	0
Counterparty D [Member] | Other Current Liabilities [Member]
Summary of gross liability balances of derivative instruments
Gross amounts of recognized liabilities	68	0
Gross amounts netted in the consolidated balance sheet	(15)	0
Net amounts of liabilities presented in the condensed consolidated balance sheet	53	0
Derivative Asset, Fair Value, Subject to Master Netting, Gross Asset Basis	0	0
Counterparty D [Member] | Other Noncurrent Liabilities [Member]
Summary of gross liability balances of derivative instruments
Gross amounts of recognized liabilities	0	0
Gross amounts netted in the consolidated balance sheet	0	0
Net amounts of liabilities 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 Liabilities [Member]
Summary of gross liability balances of derivative instruments
Gross amounts of recognized liabilities	494
Gross amounts netted in the consolidated balance sheet	(232)
Net amounts of liabilities presented in the condensed consolidated balance sheet	262
Derivative Asset, Fair Value, Subject to Master Netting, Gross Asset Basis	0
Counterparty E [Member] | Other Noncurrent Liabilities [Member]
Summary of gross liability balances of derivative instruments
Gross amounts of recognized liabilities	328
Gross amounts netted in the consolidated balance sheet	(328)
Net amounts of liabilities presented in the condensed consolidated balance sheet	0
Derivative Asset, Fair Value, Subject to Master Netting, Gross Asset Basis	$ 0