Common Shares (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		3 Months Ended
	Feb. 19, 2016	Mar. 31, 2016	Mar. 31, 2015
Common shares
Issuance of common shares for stock options exercised (in shares)		0	20
Proceeds from stock options exercised			$ 200
Common shares withheld by company		200	600
Common shares fair value		$ 1,900	$ 7,100
Common stock dividend declared (in dollars per share)	$ 0.06
Cash dividends paid		$ 16,922	$ 17,470
Common Shares
Shares repurchased		300
Total aggregate amount of shares purchased		$ 1,687