Share-Based Compensation Plans - Changes in Nonvested Stock Options (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
SHARES
Nonvested stock options outstanding, at beginning of the year (in shares)	757,738
Granted (in shares)	0
Vested (in shares)	(372,799)
Forfeited or Cancelled (in shares)	0
Nonvested stock options outstanding, at end of the year (in shares)	384,939	757,738
WEIGHTED- AVERAGE GRANT-DATE FAIR VALUE PER SHARE
Nonvested stock options weighted average grant date fair value at beginning of the year (in dollars per share)	$ 17.36
Granted (in dollars per share)	0	$ 0	$ 19.18
Vested (in dollars per share)	17.26
Forfeited or Cancelled (in dollars per share)	0
Nonvested stock options weighted average grant date fair value at end of the year (in dollars per share)	$ 17.45	$ 17.36