Changes in Goodwill by Reportable Segment (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended				12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2012 Western	Dec. 31, 2010 Western	Dec. 31, 2012 Central	Dec. 31, 2011 Central		Dec. 31, 2012 Eastern	Dec. 31, 2011 Eastern		Dec. 31, 2012 Exploration and Production
Goodwill [Line Items]
Goodwill, Beginning Balance	$ 1,116,888	$ 927,852	$ 313,038	$ 313,038	$ 424,223	$ 305,774		$ 379,627	$ 309,040
Goodwill transferred						111,806	[1]		(111,806)	[1]
Goodwill acquired	520,166	189,036	60,105		6,686	6,643		934	182,393		452,441
Goodwill divested	(497)				(497)
Goodwill, Ending Balance	$ 1,636,557	$ 1,116,888	$ 373,143	$ 313,038	$ 430,412	$ 424,223		$ 380,561	$ 379,627		$ 452,441

[1] In April 2011, as a result of the County Waste acquisition described in Note 3, the Company realigned its reporting structure and changed its three geographic operating segments from Western, Central and Southern to Western, Central and Eastern. Additionally, the Company realigned certain of the Company's districts between operating segments. This realignment resulted in the reallocation of goodwill among its segments, which is reflected in the "Goodwill transferred" line item.