Capital Stock - Summary Changes in Common Shares Outstanding (Detail) - shares	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Class of Stock [Line Items]
Common Shares Outstanding, Beginning Balance	93,622,934
Treasury stock purchases	(15,679)	(3,785,658)
Common Shares Outstanding, Ending Balance	94,461,576	93,622,934
Common Stock [Member]
Class of Stock [Line Items]
Common Shares Outstanding, Beginning Balance	93,622,934	96,380,102	119,515,894
Issuance of restricted stock and restricted stock units	564,729	589,736
Treasury stock purchases	(15,679)	(3,785,658)	(23,379,567)
Issuance of shares to directors		13,249
Vesting of restricted stock and restricted stock units	74,292
Exercise of stock options	215,300	425,505	243,775
Common Shares Outstanding, Ending Balance	94,461,576	93,622,934	96,380,102