Shareholders' Equity (Narrative) (Detail) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended		2 Months Ended	3 Months Ended						5 Months Ended	6 Months Ended	9 Months Ended		52 Months Ended
	Oct. 31, 2019	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2020	Jul. 31, 2020	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Jul. 23, 2020	Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum number of shares authorized for repurchase															13,144,773
Share repurchase plan expiration date			Aug. 09, 2021
Daily repurchase of shares, maximum											112,638
Average daily trading volume during period											450,555
Repurchase of common stock (shares)												1,271,977	0
Aggregate cost of stock repurchased						$ 105,654						$ 105,654
Maximum remaining number of shares available for repurchase			11,912,497	11,912,497						11,912,497		11,912,497		11,912,497
Cash dividend per share	$ 0.185	$ 0.16		$ 0.185			$ 0.160					$ 0.555	$ 0.480
Cash dividend per common share, increase	$ 0.025
Cash dividends on common stock				$ 49,009	$ 48,894	$ 48,018	$ 42,133	$ 42,131	$ 42,084			$ 145,921	$ 126,348
Employee Share Purchase Plan 2020 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Minimum percent of eligible compensation to purchase shares			1.00%	1.00%						1.00%		1.00%		1.00%
Maximum percent of eligible compensation to purchase shares			10.00%	10.00%						10.00%		10.00%		10.00%
Maximum number of share authorized to be issued under plan			1,000,000	1,000,000						1,000,000		1,000,000		1,000,000
Number of common shares purchased under plan										0
Minimum [Member] | Employee Share Purchase Plan 2020 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise price percentage of closing price of common shares										85.00%
Maximum [Member] | Employee Share Purchase Plan 2020 [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise price percentage of closing price of common shares										95.00%
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average grant-date fair value of award												$ 101.80
Units granted in period												326,045
Vested deferred RSUs outstanding		247,999	178,119	178,119			247,999			178,119		178,119	247,999	178,119
Restricted Stock Units (RSUs) [Member] | Progressive Waste Solutions Ltd. [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Units granted in period														0
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average grant-date fair value of award												$ 87.19
Performance period end date												Dec. 31, 2022
Units granted in period												211,987
Performance Shares [Member] | 2020 Performance-Based Restricted Share Units Plan One [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period of award												3 years
Performance Shares [Member] | 2020 Performance-Based Restricted Share Units Plan Two [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period of award												3 years
Performance Shares [Member] | Minimum [Member] | 2020 Performance-Based Restricted Share Units Plan Two [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period of award												1 year
Performance Shares [Member] | Maximum [Member] | 2020 Performance-Based Restricted Share Units Plan Two [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period of award												4 years
Employee Stock Option [Member] | Progressive Waste Solutions Ltd. [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options granted in period														0
Deferred Share Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average grant-date fair value of award												$ 103.81
Units granted in period												2,616
Vested deferred RSUs outstanding			21,586	21,586						21,586		21,586		21,586		18,970
Progressive Waste Solutions Ltd. [Member] | Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vested deferred RSUs outstanding			66,554	66,554						66,554		66,554		66,554		73,884