Earnings Per Share - Earnings (Loss) Per Common Share (Detail) - $ / shares	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Earnings Per Share [Abstract]
Earnings per common share-basic	$ 0.54	$ 0.40	$ 1.18	$ 0.94
Earnings per common share-diluted	$ 0.52	$ 0.39	$ 1.16	$ 0.92