Capital Stock - Schedule of Change in Treasury Shares (Detail) - shares	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Stockholders Equity Note [Abstract]
Beginning balance	9,665	14,967	30,547
Rabbi trust shares distributed and/or sold	(1,532)	(5,302)	(15,580)
Shares repurchased	1,800,000	0	0
Ending balance	1,808,133	9,665	14,967

Number of shares that have been repurchased during the period and have not been retired and are not held in treasury. Some state laws may govern the circumstances under which an entity may acquire its own stock and prescribe the accounting treatment therefore. This element is used when state law does not recognize treasury stock.

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Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration