Common Shares (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		6 Months Ended
	Apr. 24, 2015	Jun. 30, 2015	Jun. 30, 2014
Common shares
Issuance of common shares for stock options exercised (in shares)		100	2,900
Proceeds from stock options exercised		$ 1,200	$ 29,000
Common shares withheld by company		600	300
Common shares fair value		$ 7,400	$ 7,300
Common stock dividend declared (in dollars per share)	$ 0.06
Cash dividends paid		$ 34,980	$ 23,792