Loans and Allowance for Credit Losses - Summary of Changes in Accretable Discount for ACI Loans (Details) - ACI Loans - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Financing Receivable Recorded Investment [Line Items]
Balance at beginning of period	$ 67,405	$ 78,422
Additions (See Note 2)	42,626
Accretion	(5,844)	(5,192)
Reclass from nonaccretable difference due to increases in expected cash flow	899	4,558
Other changes, net	(6,843)	(1,714)
Balance at end of period	$ 98,243	$ 76,074