Derivative Instruments and Balance Sheet Offsetting - Notional Amount and Fair Value (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Derivative instruments
Notional Amount	$ 4,403,278	$ 3,516,418
Gross Derivative Assets	73,068	38,595
Gross Derivative Liabilities	97,179	32,379
Credit valuation adjustments for counterparty credit risk	1,500	901
Derivatives designated as hedging instruments:
Derivative instruments
Notional Amount	1,145,000	820,000
Gross Derivative Assets	606	10,148
Gross Derivative Liabilities	25,060	3,278
Derivatives designated as hedging instruments: \| Interest rate swaps
Derivative instruments
Notional Amount	1,145,000	820,000
Gross Derivative Assets	606	10,148
Gross Derivative Liabilities	25,060	3,278
Derivatives not designated as hedging \| Total customer-initiated and mortgage banking derivatives
Derivative instruments
Notional Amount	3,258,278	2,696,418
Gross Derivative Assets	72,462	28,447
Gross Derivative Liabilities	72,119	29,101
Derivatives not designated as hedging \| Customer-initiated derivatives
Derivative instruments
Notional Amount	2,908,127	2,477,640
Gross Derivative Assets	69,024	26,680
Gross Derivative Liabilities	70,707	27,664
Derivatives not designated as hedging \| Forward contracts related to mortgage loans to be delivered for sale
Derivative instruments
Notional Amount	165,772	127,159
Gross Derivative Assets	0	0
Gross Derivative Liabilities	661	719
Derivatives not designated as hedging \| Interest rate lock commitments
Derivative instruments
Notional Amount	149,084	54,848
Gross Derivative Assets	2,687	1,049
Gross Derivative Liabilities	0	0
Derivatives not designated as hedging \| Power Equity CD
Derivative instruments
Notional Amount	35,295	36,771
Gross Derivative Assets	751	718
Gross Derivative Liabilities	$ 751	$ 718

Aggregate notional amount specified by the derivative(s). Expressed as an absolute value.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Article 12
-Section 13
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