Annual report pursuant to Section 13 and 15(d)

Derivative Instruments and Hedging Activities Credit Risk - Counterparty Exposure (Details)

v2.4.1.9
Derivative Instruments and Hedging Activities Credit Risk - Counterparty Exposure (Details) (USD $)
In Thousands, unless otherwise specified
Dec. 31, 2014
Dec. 31, 2013
Derivatives, Fair Value [Line Items]    
Derivative assets $ 380,791us-gaap_DerivativeFairValueOfDerivativeAsset $ 549,859us-gaap_DerivativeFairValueOfDerivativeAsset
Derivative liabilities 90,233us-gaap_DerivativeFairValueOfDerivativeLiability 22,081us-gaap_DerivativeFairValueOfDerivativeLiability
Collateral Securities Repledged, Delivered, or Used (71,436)us-gaap_CollateralSecuritiesRepledgedDeliveredOrUsed  
Collateral Already Posted, Aggregate Fair Value $ 216,430us-gaap_CollateralAlreadyPostedAggregateFairValue