For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

Quarterly Results (Unaudited) (Parenthetical) (Detail)	3 Months Ended		12 Months Ended
Quarterly Results (Unaudited) (Parenthetical) (Detail)	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Revenues \| Airfreight services
Concentration Risk [Line Items]
Percentage increase of air revenues	41.00%
Revenues \| Peoples Republic Of China Including Hong Kong \| Geographic Concentration Risk
Concentration Risk [Line Items]
Concentration percentage	34.00%	25.00%	32.00%	26.00%	29.00%
Revenues \| Peoples Republic Of China Including Hong Kong \| Airfreight services \| Geographic Concentration Risk
Concentration Risk [Line Items]
Concentration percentage	49.00%
Operating Income \| Peoples Republic Of China Including Hong Kong \| Geographic Concentration Risk
Concentration Risk [Line Items]
Concentration percentage	27.00%	25.00%	29.00%	27.00%	30.00%