Derivative Financial Instruments Impact of Netting Agreements (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Derivative Asset:
Derivative assets, gross	$ 281,193	$ 300,314
Effect of master netting agreements	(2,548)	(29)
Derivative asset, net	278,645	300,285
Derivative Liability:
Derivative liability, gross	2,968	767
Effect of master netting agreements	(2,548)	(29)
Derivative liability, net	$ 420	$ 738