Summary of Offsetting Assets and Liabilities Summary of Offsetting Assets and Liabilities - Netting Arrangements (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Derivative instruments (assets)
Gross fair value of recognized assets	$ 72,217	$ 119,862
Financial instruments	56,224	26,254
Cash collateral	(14,263)	(92,756)
Net fair value	1,730	852
Securities purchased under agreements to resell, gross	20,900
Securities purchased under agreements to resell, not offset	20,900
Securities purchased under agreements to resell, collateral, obligation to return cash	0
Securities purchased under agreements to resell, offset against collateral, net of not subject to master netting arrangement, policy election	0
Derivative asset, securities purchased under agreements to resell, securities borrowed	93,117
Derivative asset, securities purchased under agreements to resell, securities borrowed, not offset	77,124
Derivative asset, securities purchased under agreements to resell, securities borrowed, collateral, obligation to return cash	(14,263)
Derivative asset, securities purchased under agreements to resell, securities borrowed, amount offset against collateral	1,730
Derivatives instrument (liabilities)
Gross fair value of recognized liabilities	70,720	26,254
Financial instruments	56,224	26,254
Amount of unrestricted cash collateral to counterparties in the normal course of business	13,006	0
Net fair value	$ 1,490	$ 0

Fair value, after effects of master netting arrangements, deduction of assets not subject to a master netting arrangement and elected not to be offset, of 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, offset against an obligation to return collateral.

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Fair value of 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, elected not to be offset, deducted from derivative assets.