Shareholders' Equity (Narrative) (Detail) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended		3 Months Ended		6 Months Ended	8 Months Ended	46 Months Ended
	Oct. 31, 2019	Sep. 30, 2019	Mar. 31, 2020	Mar. 31, 2019	Jul. 31, 2019	Mar. 31, 2020	Mar. 31, 2020	Dec. 31, 2019	Jul. 25, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Maximum number of shares authorized for repurchase									13,184,474
Share repurchase plan expiration date						Aug. 07, 2020
Daily repurchase of shares, maximum					79,933
Average daily trading volume during period					319,734
Repurchase of common stock (shares)			1,271,977	0
Aggregate cost of stock repurchased			$ 105,654
Maximum remaining number of shares available for repurchase			11,912,497			11,912,497	11,912,497
Cash dividend per share	$ 0.185	$ 0.16	$ 0.185	$ 0.160
Cash dividend per common share, increase	$ 0.025
Cash dividends on common stock			$ 48,018	$ 42,084
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			190,201	249,003		190,201	190,201
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	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	73,884