Goodwill and Core Deposit Intangibles - CDI Roll Forward (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Gross Balance of CDI:
Balance, beginning of year	$ 125,945	$ 54,809	$ 15,102
Additions due to acquisitions	0	71,136	39,707
Balance, end of year	125,945	125,945	54,809
Accumulated amortization:
Balance, beginning of year	(25,389)	(11,795)	(5,651)
Amortization	(17,245)	(13,594)	(6,144)
Balance, end of year	(42,633)	(25,389)	(11,795)
Net CDI, end of year	$ 83,312	$ 100,556	$ 43,014