(Schedule of Goodwill by Reportable Business Segment) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Goodwill [Line Items]
Goodwill gross value			$ 390,196us-gaap_GoodwillGross
Accumulated impairment losses			(92,423)
Carrying value at	386,416us-gaap_Goodwill	341,382us-gaap_Goodwill
Goodwill [Roll Forward]
Carrying value at	341,382us-gaap_Goodwill	297,773us-gaap_Goodwill
Acquisitions	53,803us-gaap_GoodwillAcquiredDuringPeriod	46,741us-gaap_GoodwillAcquiredDuringPeriod
Adjustments to prior acquisitions	(1,184)
Impact of currency fluctuations	(7,585)us-gaap_GoodwillTranslationAdjustments	(3,132)us-gaap_GoodwillTranslationAdjustments
Carrying value at	386,416us-gaap_Goodwill	341,382us-gaap_Goodwill
North America
Goodwill [Line Items]
Goodwill gross value			364,563
Accumulated impairment losses			(92,423)
Carrying value at	336,088	285,734
Goodwill [Roll Forward]
Carrying value at	285,734	272,140
Acquisitions	52,883	15,049
Adjustments to prior acquisitions	(625)
Impact of currency fluctuations	(1,904)	(1,455)
Carrying value at	336,088	285,734
Europe
Goodwill [Line Items]
Goodwill gross value			20,216
Accumulated impairment losses			0
Carrying value at	44,433	49,204
Goodwill [Roll Forward]
Carrying value at	49,204	20,216
Acquisitions	920	29,941
Adjustments to prior acquisitions	(459)
Impact of currency fluctuations	(5,232)	(953)
Carrying value at	44,433	49,204
Asia Pacific
Goodwill [Line Items]
Goodwill gross value			5,417
Accumulated impairment losses			0
Carrying value at	5,895	6,444
Goodwill [Roll Forward]
Carrying value at	6,444	5,417
Acquisitions	0	1,751
Adjustments to prior acquisitions	(100)
Impact of currency fluctuations	(449)	(724)
Carrying value at	$ 5,895	$ 6,444

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

-URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13816-109267

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 350

-SubTopic 20

-Section 45

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6388280&loc=d3e13770-109266

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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

-Publisher FASB

-Name Accounting Standards Codification

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