Derivatives (Risk Participation Agreement) (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Derivative [Line Items]
Derivative liabilities	$ 114,542	$ 74,935
Derivative assets	81,456	66,146
Derivatives not designated as hedging instruments
Derivative [Line Items]
Notional amount	12,295,137	10,153,108
Derivative liabilities	105,895	68,136
Derivative assets	79,140	66,146
Derivatives not designated as hedging instruments | RPAs
Derivative [Line Items]
Notional amount	118,024	49,033
Derivative liabilities	77	8
Derivative assets	1	1
Derivatives not designated as hedging instruments | RPAs | Long
Derivative [Line Items]
Notional amount	105,800	35,200
Derivative liabilities	77	8
Derivative assets	0	0
Derivatives not designated as hedging instruments | RPAs | Short
Derivative [Line Items]
Notional amount	12,300	13,800
Derivative liabilities	0	0
Derivative assets	$ 1	$ 1