Capital Stock - Schedule of Change in Treasury Shares (Detail) - shares	3 Months Ended	6 Months Ended
Jun. 30, 2021	Jun. 30, 2021
Stockholders Equity Note [Abstract]
Beginning balance	10,004,683	10,005,795
Rabbi trust shares distributed/sold	0	(1,112)
Shares repurchased	0	0
Ending balance	10,004,683	10,004,683

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