Derivative Instruments - Non-hedge Derivatives (Details) - Not Designated as Hedging Instrument - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Derivative [Line Items]
Description of Location of Gain (Loss) on Interest Rate Derivative on Income Statement	Other noninterest income
Derivative, Gain (Loss) on Derivative, Net	$ (13)	$ (20)
Notional Amount	2,193,298		$ 2,119,448
Estimated Fair Value	$ (141)		(128)
Assets
Derivative [Line Items]
Description of Location of Interest Rate Derivatives on Balance Sheet	Other assets
Notional Amount	$ 1,096,649		1,059,724
Estimated Fair Value	$ 24,555		22,273
Liabilities
Derivative [Line Items]
Description of Location of Interest Rate Derivatives on Balance Sheet	Other liabilities
Notional Amount	$ 1,096,649		1,059,724
Estimated Fair Value	$ (24,696)		$ (22,401)