Earnings per Share - Common Stock Equivalents Not Included in Computation of Diluted Earnings Per Share (Detail) - $ / shares	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Restricted Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	22,802	72,432
Restricted Stock Units [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	22,750	0
Minimum [Member] | Restricted Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Net Income, Per Outstanding Unit, Amount	$ 8.55	$ 8.38
Minimum [Member] | Restricted Stock Units [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Net Income, Per Outstanding Unit, Amount	15.09	0.00
Maximum [Member] | Restricted Stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Net Income, Per Outstanding Unit, Amount	13.96	10.09
Maximum [Member] | Restricted Stock Units [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive Securities Excluded from Computation of Net Income, Per Outstanding Unit, Amount	$ 15.09	$ 0.00