Derivative Instruments - Balance sheet offsetting (Details) - USD ($) $ in Thousands		Dec. 31, 2015	Dec. 31, 2014
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative assets - gross amounts recognized in the balance sheet		$ 89,314	$ 136,659
Derivative assets - gross amounts offset in the balance sheet	[1]	3,087	696
Derivative assets - net amounts in the balance sheet		86,227	135,963
Derivative assets - financial instruments not offset in the balance sheet		0	0
Derivative assets - cash collateral not offset in the balance sheet		30,958	78,580
Derivative assets - net amount		55,269	57,383
Derivative liabilities - gross amounts recognized in the balance sheet		45,495	31,184
Derivative liabilities - gross amounts offset in the balance sheet	[1]	3,087	696
Derivative liabilities - net amounts in the balance sheet		42,408	30,488
Derivative liabilities - financial instruments not offset in the balance sheet		0	0
Derivative liabilities - cash collateral not offset in the balance sheet		0	0
Derivative liabilities - net amount		$ 42,408	$ 30,488

[1] Other assets and other liabilities include derivative instruments. The derivative balances included in each category are reported on a gross basis by level with a netting adjustment presented separately in the Collateral and Counterparty Netting column. The fair values of the individual derivative contracts are reported gross in their respective levels based on the fair value hierarchy. For further details regarding derivative fair values and associated collateral received or paid see