Securities - Additional Information (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Investments, Debt and Equity Securities [Abstract]
Available-for-sale securities pledged	$ 1,500,000,000		$ 1,500,000,000		$ 1,200,000,000
Held-to-maturity securities pledged as collateral	0		0		$ 0
Realized gains on securities available-for-sale	0	$ 0	0	$ 0
Proceeds from sales of securities available-for-sale	93,300,000		93,332,000	0
Other-than-temporary securities impairment (OTTI)	$ 0	$ 0	$ 0	$ 0