Condensed Consolidated Statements of Shareholders' Equity (Parenthetical) - $ / shares			3 Months Ended		9 Months Ended
	Aug. 06, 2018	Aug. 08, 2017	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Statement of Stockholders' Equity [Abstract]
Common shares repurchased (in shares)					500,989	612,034
Repurchase of common shares, weighted average price (in dollars per share)					$ 59.83	$ 59.75
Stock divided declared			15.00%		15.00%
Dividend declared per common share (in dollars per share)	$ 0.27	$ 0.23	$ 0.27	$ 0.23	$ 0.81	$ 0.70