Capital Stock - Additional Information (Detail) - $ / shares	3 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016
Class Of Stock Disclosures [Abstract]
Common dividends declared per share	$ 0.02	$ 0.02	$ 0.02	$ 0.02	$ 0.02	$ 0.02	$ 0.02	$ 0.02	$ 0.02	$ 0.02	$ 0.02	$ 0.02
Authorized capital stock	485,000,000				485,000,000
Common stock, shares authorized	475,000,000				475,000,000
Preferred stock, shares authorized	10,000,000				10,000,000