Shareholders' Equity - Narrative (Detail)	1 Months Ended	12 Months Ended
	Jan. 31, 2019 $ / shares shares	Dec. 31, 2018 $ / shares shares	Dec. 31, 2017 shares	Dec. 31, 2019 series $ / shares	Nov. 30, 2013
Capital Unit [Line Items]
Percent of outstanding shares authorized for repurchase					5.00%
Premium percent over current book value					20.00%
Repurchase of common shares (shares) | shares	31,159	719,200	0
Weighted-average exercise price, outstanding (usd per share)	$ 18.35	$ 18.04
Number of preferred stock series outstanding | series				4
Fixed-to-Floating Rate Non-Cumulative Perpetual Preferred Stock, Series C, par value $1.00 per share
Capital Unit [Line Items]
Preferred stock, redemption price (usd per share)				$ 25.00