Schedule of Fair Value of All Futures Contracts (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Derivative [Line Items]
Total fair market value of Futures Contracts	$ (42,967)	$ (25,585)
Futures Contracts Designed to Replicate Swaps
Derivative [Line Items]
Total fair market value of Futures Contracts	(45,537)	(27,881)
Futures Contracts Designed to Hedge Value Changes in Forward Purchases
Derivative [Line Items]
Total fair market value of Futures Contracts	$ 2,570	$ 2,296

Fair value portion of liability contracts related to the exchange of different currencies, including, but not limited to, foreign currency options, forward (delivery or nondelivery) contracts, and swaps entered into.

No definition available.

Name:	us-gaap_ForeignCurrencyContractsLiabilityFairValueDisclosure
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant