Subsequent Events (Details) - Common Shares - USD ($) $ / shares in Units, $ in Millions	1 Months Ended	3 Months Ended
	Apr. 28, 2017	Mar. 31, 2017
Subsequent Event [Line Items]
Common shares repurchased during period, Number of shares (in shares)		550,000
Common shares repurchased during period, Aggregate amount		$ 80.0
Common shares repurchased during period, Average cost (in usd per share)		$ 145.36
Subsequent Event
Subsequent Event [Line Items]
Common shares repurchased during period, Number of shares (in shares)	163,106
Common shares repurchased during period, Aggregate amount	$ 22.8
Common shares repurchased during period, Average cost (in usd per share)	$ 139.71