Segment Reporting (Changes in Goodwill by Reportable Segment) (Detail) - USD ($) $ in Thousands	9 Months Ended
Sep. 30, 2018	Sep. 30, 2017
Goodwill [Line Items]
Goodwill, Beginning Balance	$ 4,681,774	$ 4,390,261
Goodwill acquired	169,950	309,031
Goodwill divested		(36,486)
Impairment loss		(77,343)
Goodwill adjustment for assets sold		2,526
Goodwill adjustment for assets held for sale	10,194	(11,080)
Impact of changes in foreign currency	(48,622)	111,439
Goodwill, Ending Balance	4,813,296	4,688,348
Southern [Member]
Goodwill [Line Items]
Goodwill, Beginning Balance	1,436,320	1,470,023
Goodwill acquired	4,800	7,484
Goodwill divested		(31,543)
Goodwill adjustment for assets sold		2,205
Goodwill adjustment for assets held for sale	10,194	(11,080)
Goodwill, Ending Balance	1,451,314	1,437,089
Western [Member]
Goodwill [Line Items]
Goodwill, Beginning Balance	397,508	376,537
Goodwill acquired	666	20,906
Goodwill, Ending Balance	398,174	397,443
Eastern [Member]
Goodwill [Line Items]
Goodwill, Beginning Balance	804,133	533,160
Goodwill acquired	122,136	272,501
Goodwill divested		(4,276)
Goodwill adjustment for assets sold		321
Goodwill, Ending Balance	926,269	801,706
Canada [Member]
Goodwill [Line Items]
Goodwill, Beginning Balance	1,575,538	1,465,274
Goodwill acquired	151	7,127
Impact of changes in foreign currency	(48,622)	111,439
Goodwill, Ending Balance	1,527,067	1,583,840
Central [Member]
Goodwill [Line Items]
Goodwill, Beginning Balance	468,275	467,924
Goodwill acquired	42,197	1,013
Goodwill divested		(667)
Goodwill, Ending Balance	$ 510,472	468,270
Exploration and Production [Member]
Goodwill [Line Items]
Goodwill, Beginning Balance		77,343
Goodwill acquired
Goodwill divested
Impairment loss		(77,343)
Goodwill adjustment for assets sold
Goodwill adjustment for assets held for sale
Impact of changes in foreign currency
Goodwill, Ending Balance

Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 50
-Paragraph 1
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-URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13816-109267

Reference 2: http://www.xbrl.org/2003/role/presentationRef
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