Goodwill and Other Intangible Assets (Tables)

12 Months Ended

Dec. 31, 2017

Goodwill and Intangible Assets Disclosure [Abstract]

Schedule of Goodwill

The changes in goodwill by reportable segment are as follows:

(in millions)	Corporate		Small Business(2)		Public		Other(4)			Consolidated
Balance at December 31, 2014(1)	$	1,045.9	$	185.9	$	911.3	$	74.5		$	2,217.6
Foreign currency translation	—		—		—		(22.4		)	(22.4		)
Acquisition	—		—		—		305.2			305.2
Balance at December 31, 2015(1)	1,045.9		185.9		911.3		357.3			2,500.4
Foreign currency translation	—		—		—		(45.4		)	(45.4		)
CDW Advanced Services Allocation(3)	28.2		—		18.3		(46.5		)	—
Balance at December 31, 2016(1)	1,074.1		185.9		929.6		265.4			2,455.0
Foreign currency translation	—		—		—		24.6			24.6
Balances as of December 31, 2017(1)	$	1,074.1	$	185.9	$	929.6	$	290.0		$	2,479.6

(1) Goodwill is net of accumulated impairment losses of $1,571 million, $354 million and $28 million related to the Corporate, Public and Other segments, respectively.

(2) Amounts have been recast to present Small Business as its own operating and reportable segment.

(3) Effective January 1, 2016, the CDW Advanced Services business is included in the Company's Corporate and Public segments.

(4) Other is comprised of Canada and CDW UK operating segments.

Schedule of Finite-Lived Intangible Assets

The following table shows estimated useful lives of definite-lived intangible assets:

Classification	Estimated Useful Lives
Customer relationships and contracts	3 to 14 years
Trade name	generally 20 years
Internally developed software	3 to 5 years
Other	1 to 10 years

A summary of intangible assets is as follows:

(in millions)
December 31, 2017	Gross Carrying Amount		Accumulated Amortization			Net Carrying Amount
Customer relationships and contracts	$	2,106.8	$	(1,490.8	)	$	616.0
Trade name	422.2		(216.3		)	205.9
Internally developed software	162.6		(89.6		)	73.0
Other	2.9		(0.8		)	2.1
Total	$	2,694.5	$	(1,797.5	)	$	897.0
December 31, 2016
Customer relationships and contracts	$	2,084.6	$	(1,322.7	)	$	761.9
Trade name	422.1		(195.2		)	226.9
Internally developed software	142.6		(77.7		)	64.9
Other	6.0		(4.1		)	1.9
Total	$	2,655.3	$	(1,599.7	)	$	1,055.6

Schedule of Finite-Lived Intangible Assets, Future Amortization Expense

Estimated future amortization expense related to intangible assets is as follows:

(in millions)
Years ending December 31,	Estimated Future Amortization Expense
2018	$	219.8
2019	201.4
2020	167.6
2021	72.3
2022	38.4
Thereafter	197.5
Total future amortization expense	$	897.0