Changes in Carrying Amount of Goodwill (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended	12 Months Ended
	Dec. 31, 2018	Mar. 31, 2017	Jun. 30, 2017	Dec. 31, 2018	Jun. 30, 2018	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2016
Goodwill [Line Items]
Goodwill, Impaired, Accumulated Impairment Loss	$ (33,244)			$ (33,244)
Goodwill [Roll Forward]
Beginning balance		$ 3,054,769	$ 3,054,769	3,536,511		$ 3,054,769		$ 2,319,246
Business acquisitions and adjustments to previously recorded goodwill				972,890		314,817		842,809
Impairment of goodwill	(33,000)			(33,244)		0		0
Exchange rate effects				(94,699)		166,925		(107,286)
Ending balance	4,381,458			4,381,458		3,536,511		3,054,769
North America
Goodwill [Line Items]
Goodwill, Impaired, Accumulated Impairment Loss	(33,244)			(33,244)
Goodwill [Roll Forward]
Beginning balance		1,661,800	1,661,800	1,709,354		1,661,800		1,433,499
Business acquisitions and adjustments to previously recorded goodwill				6,805		39,836		226,483
Impairment of goodwill				(33,244)
Exchange rate effects				(9,383)		7,718		1,818
Ending balance	1,673,532			1,673,532		1,709,354		1,661,800
Europe
Goodwill [Line Items]
Goodwill, Impaired, Accumulated Impairment Loss	$ 0			$ 0
Amount that fair value exceeds carrying value	15.00%			15.00%
Goodwill [Roll Forward]
Beginning balance		1,099,976	1,099,976	$ 1,414,898		1,099,976		594,482
Business acquisitions and adjustments to previously recorded goodwill				970,923		155,366		614,437
Impairment of goodwill				0
Exchange rate effects				(85,532)		159,556		(108,943)
Ending balance	$ 2,300,289			2,300,289		1,414,898		1,099,976
Specialty
Goodwill [Line Items]
Goodwill, Impaired, Accumulated Impairment Loss	0			0
Goodwill [Roll Forward]
Beginning balance		292,993	292,993	412,259		292,993		291,265
Business acquisitions and adjustments to previously recorded goodwill				(4,838)		119,615		1,889
Impairment of goodwill				0
Exchange rate effects				216		(349)		(161)
Ending balance	407,637			407,637		$ 412,259		292,993
Stahlgruber [Member]
Goodwill [Line Items]
Goodwill, Acquired During Period				908,000
Goodwill [Roll Forward]
Ending balance	$ 908,253			$ 908,253
PGW
Goodwill [Line Items]
Goodwill, Acquired During Period			$ 3,000		$ 208,000			205,000
Rhiag
Goodwill [Line Items]
Goodwill, Acquired During Period		$ 5,000					$ 591,000	$ 585,000