Investment Securities - Additional Information (Details)	3 Months Ended
	Mar. 31, 2019 USD ($) security	Mar. 31, 2018 USD ($)	Dec. 31, 2018 security
Investment Securities [Line Items]
Number of security positions in the securities held to maturity portfolio in an unrealized loss position (in security) | security	268		378
Fair value of investments held to maturity pledged as collateral	$ 1,200,000,000
Weighted-average remaining expected life of residential mortgage-backed securities held to maturity, years	8 years
Number of security positions in the securities available for sale portfolio in an unrealized loss position (in security) | security	449		545
Fair value of securities available for sale pledged as collateral	$ 1,100,000,000
Weighted-average remaining expected life of residential mortgage-backed securities available for sale, years	8 years 3 months 18 days
Other than temporary impairment losses recognized in earnings	$ 0	$ 0
Losses on securities transactions, net	$ 32,000	$ 765,000
Single Issuer Trust Preferred Securities | Non-Rated
Investment Securities [Line Items]
Number of security positions in the securities held to maturity portfolio in an unrealized loss position (in security) | security	4