Goodwill (Tables)

3 Months Ended

Mar. 31, 2018

Goodwill and Intangible Assets Disclosure [Abstract]

Summary of Goodwill

The following table summarizes goodwill at the balance sheet dates:

(in millions)	Total
At December 31, 2017
Gross cost (1)	$	598.3
Accumulated impairment losses		(236.5	)
Net book amount	$	361.8
Exchange effect		2.3
At March 31, 2018
Gross cost (1)	$	600.6
Accumulated impairment losses		(236.5	)
Net book amount	$	364.1

⁽¹⁾  Gross cost for 2018 and 2017 is net of $298.5 million of historical accumulated amortization.