Shareholders' Equity (Schedule Of Share Repurchases) (Details) - USD ($) $ / shares in Units, $ in Millions			12 Months Ended
	May 06, 2015	May 01, 2014	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Class of Stock [Line Items]
Stock repurchase program, authorized amount		$ 500.0
Treasury shares reserved for issuance under stock compensation plans		3,000,000
Shares repurchased, shares			4,669,513	6,047,437	4,906,785
Cost of shares repurchased			$ 166.3	$ 245.3	$ 175.4
Shares repurchased, average price per share			$ 35.61	$ 40.56	$ 35.74
Exor SA
Class of Stock [Line Items]
Shares repurchased, shares	4,053,537
Cost of shares repurchased	$ 164.4
Shares repurchased, average price per share	$ 40.546