Summary of Significant Accounting Policies (Narrative) (Details)	12 Months Ended
	Dec. 31, 2018 USD ($) pension_plan segment landfill	Dec. 31, 2017 USD ($) segment	Dec. 31, 2016 USD ($) segment	Jan. 01, 2019 USD ($)	Oct. 01, 2018
Concentration Risk [Line Items]
Net book credit balances in our primary disbursement accounts	$ 64,800,000	$ 53,200,000
Restricted cash and marketable securities	108,100,000	141,100,000	$ 90,500,000
Capitalized interest	$ 6,800,000	$ 6,500,000	$ 6,200,000
Post-closure period	30 years
Number of closed landfills | landfill	129
Asset retirement obligation, costs to discharge, inflation rate	1.70%	1.70%	1.80%
Years of historical moving average increase of the U.S. Consumer Price Index used as our basis for inflation rate	10 years
Number of reportable segments | segment	2	2	2
Future estimates of revenue and expense growth rate	3.00%
Future estimated effective tax rates	27.00%
Estimated discount rates, minimum range	7.00%
Estimated discount rates, maximum range	8.00%
Number of reporting units | segment	2
Fair value of our reporting units exceeded the carrying value of our reporting units, maximum range					110.00%
Number of qualified defined pension plans | pension_plan	1
Minimum
Concentration Risk [Line Items]
Interest capitalization, construction costs threshold	$ 50,000
Interest capitalization, construction phase period	1 month
Interest capitalization, useful life of assets under construction	1 year
Amortization period for other intangible assets	1 year
Right-of-use liability				$ 240,000,000
Right-of-use asset				225,000,000
Maximum
Concentration Risk [Line Items]
Amortization period for other intangible assets	18 years
Right-of-use liability				270,000,000
Right-of-use asset				$ 255,000,000
Insurance Programs For Workers' Compensation
Concentration Risk [Line Items]
Restricted cash and marketable securities	$ 78,600,000