Derivative Instruments - Balance Sheet Offsetting (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative assets - gross amounts recognized in the balance sheet	$ 27,487	$ 24,842
Derivative assets - gross amounts offset in the balance sheet	1,342	1,327
Derivative assets - net amounts in the balance sheet	26,145	23,515
Derivative assets - financial instruments not offset in the balance sheet	0	0
Derivative assets - cash collateral not offset in the balance sheet	0	0
Derivative assets - net amount	26,145	23,515
Derivative liabilities - gross amounts recognized in the balance sheet	105,485	66,626
Derivative liabilities - gross amounts offset in the balance sheet	1,342	1,327
Derivative liabilities - net amounts in the balance sheet	104,143	65,299
Derivative liabilities - financial instruments not offset in the balance sheet	0	0
Derivative liabilities - cash collateral not offset in the balance sheet	19,847	12,130
Derivative liabilities - net amount	$ 84,296	$ 53,169

Fair value of liability associated with financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset.

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