Acquisitions, Intangible Assets and Goodwill (Intangible Assets) (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Finite lived intangible assets
Gross Carrying Amount	$ 688,595		$ 688,595		$ 712,487
Accumulated Amortization	(439,470)		(439,470)		(440,301)
Net Carrying Amount	249,125		249,125		272,186
Amortization expense	11,000	$ 8,000	22,000	$ 17,000
Customer relationships
Finite lived intangible assets
Gross Carrying Amount	482,092		482,092		504,716
Accumulated Amortization	(265,904)		(265,904)		(271,066)
Net Carrying Amount	216,188		216,188		233,650
Software & technology
Finite lived intangible assets
Gross Carrying Amount	166,100		166,100		167,122
Accumulated Amortization	(141,338)		(141,338)		(138,724)
Net Carrying Amount	24,762		24,762		28,398
Trademarks & other
Finite lived intangible assets
Gross Carrying Amount	40,403		40,403		40,649
Accumulated Amortization	(32,228)		(32,228)		(30,511)
Net Carrying Amount	$ 8,175		$ 8,175		$ 10,138

The aggregate expense charged against earnings to allocate the cost of intangible assets (nonphysical assets not used in production) in a systematic and rational manner to the periods expected to benefit from such assets. As a noncash expense, this element is added back to net income when calculating cash provided by or used in operations using the indirect method.

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