Derivative Financial Instruments (Details 3) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Summary of gross liability balances of derivative instruments
Gross amounts of recognized liabilities	$ 10,521	$ 10,649
Gross amounts netted in the consolidated balance sheet	(4,294)	(7,704)
Net amounts of liabilities presented in the condensed consolidated balance sheet	6,227	2,945
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 Liabilities [Member]
Summary of gross liability balances of derivative instruments
Gross amounts of recognized liabilities	2,331	2,550
Gross amounts netted in the consolidated balance sheet	(766)	(1,746)
Net amounts of liabilities presented in the condensed consolidated balance sheet	1,565	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	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 B [Member]
Summary of gross liability balances of derivative instruments
Amounts subject to master netting arrangements presented on a gross basis	0	0
Counterparty B [Member] | Other Current Liabilities [Member]
Summary of gross liability balances of derivative instruments
Gross amounts of recognized liabilities	2,282	2,136
Gross amounts netted in the consolidated balance sheet	(805)	(1,371)
Net amounts of liabilities presented in the condensed consolidated balance sheet	1,477	765
Counterparty B [Member] | Other Noncurrent Liabilities [Member]
Summary of gross liability balances of derivative instruments
Gross amounts of recognized liabilities	353	668
Gross amounts netted in the consolidated balance sheet	(353)	(668)
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 C [Member] | Other Current Liabilities [Member]
Summary of gross liability balances of derivative instruments
Gross amounts of recognized liabilities	4,765	3,996
Gross amounts netted in the consolidated balance sheet	(1,690)	(2,873)
Net amounts of liabilities presented in the condensed consolidated balance sheet	3,075	1,123
Derivative Asset, Fair Value, Subject to Master Netting, Gross Asset Basis	99	0
Counterparty C [Member] | Other Noncurrent Liabilities [Member]
Summary of gross liability balances of derivative instruments
Gross amounts of recognized liabilities	637	1,299
Gross amounts netted in the consolidated balance sheet	(637)	(1,046)
Net amounts of liabilities presented in the condensed consolidated balance sheet	0	253
Derivative Asset, Fair Value, Subject to Master Netting, Gross Asset Basis	11	0
Counterparty D [Member] | Other Current Liabilities [Member]
Summary of gross liability balances of derivative instruments
Gross amounts of recognized liabilities	153	0
Gross amounts netted in the consolidated balance sheet	(43)	0
Net amounts of liabilities presented in the condensed consolidated balance sheet	110	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