Earnings Per Share - Additional information (Detail) - shares	1 Months Ended	12 Months Ended
	Oct. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Earnings Per Share [Abstract]
Common stock repurchased	25,092,000	25,092,000	36,325,000	31,991,000