Derivative Financial Instruments Impact of Netting Agreements (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Derivative Asset:
Derivative assets, gross	$ 68,502	$ 11,177
Effect of master netting agreements	(10,974)	(10,930)
Derivative asset, net	57,528	247
Derivative Liability:
Derivative liability, gross	12,449	81,190
Effect of master netting agreements	(10,974)	(10,930)
Derivative liability, net	$ 1,475	$ 70,260

Fair value, after the effects of master netting arrangements, of a 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. Includes assets not subject to a master netting arrangement and not elected to be offset.

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