Securities - Summary of Proceeds from Sales, Gross Gains, and Gross Losses on Sales of Securities Available for Sale (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Investments Debt And Equity Securities [Abstract]
Gross realized gains									$ 816	$ 167	$ 4,172
Gross realized losses									(2,669)	(313)	(436)
Realized (losses) gains on sale of securities available for sale, net	$ (54)	$ 2	$ (1,800)	$ 12	$ 16	$ 1	$ (244)	$ 81	(1,853)	(146)	3,736
Proceeds from sales of securities available-for-sale			$ 187,800						$ 268,799	$ 161,401	$ 538,960