Landfill Accounting (Narrative) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		12 Months Ended
	Mar. 31, 2015 site	Mar. 31, 2014	Dec. 31, 2014
Landfill Accounting [Line Items]
Number of municipal solid waste landfills owned or operated by company	42
Number of owned landfills that only accept exploration and production waste	9
Number of owned landfills that only accept construction and demolition, industrial and other non-putrescible waste	8
Number of developed landfills owned and operated by company	49
Number of landfills operated, not owned, under life of site operating agreements	5
Number of landfills operated under limited-term operating agreements	5
Property and equipment, net	$ 2,597,232		$ 2,594,205
Average remaining landfill life based on permitted capacity and projected annual disposal volumes	35 years
Number of owned landfills the company is seeking to expand	7
Number of landfills operated under life-of-site operating agreements that the company is seeking to expand	2
Average remaining landfill life based on permitted capacity, projected annual disposal volumes and probable expansion capacity	41 years
Life of Company's owned landfills and landfills operated under life of site operating agreements min range	2 years
Life of Company's owned landfills and landfills operated under life of site operating agreements max range	184 years
Landfill depletion expense	18,849	19,071
Average rate per ton consumed related to landfill depletion at owned landfills and landfills operated under life of site agreements	4.13	4.20
Discount rate for purposes of computing layers for final capping, closure and post-closure obligations	4.75%		5.75%
Inflation rate for purposes of computing layers for final capping, closure and post-closure obligations	2.50%		2.50%
Accretion expense associated with landfill obligations	901	823
Average rate per ton consumed related to final capping, closure and post-closure landfill accretion expense	0.20	0.18
Restricted asset balance for purposes of securing our performance of future final capping, closure and post-closure obligations	39,336
Landfill [Member]
Landfill Accounting [Line Items]
Property and equipment, net	$ 1,718,237