Common Shares (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	12 Months Ended
	Jul. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Common shares
Common stock dividend declared (in dollars per share)	$ 0.06		$ 0.04
Cash dividends paid		$ 69,363	$ 59,145	$ 47,168
Common Shares
Shares repurchased		10,600,000	10,375,000
Share price of shares purchased (in dollars per share)			$ 24.10
Total aggregate amount of shares purchased		$ 99,598	$ 250,037
Preferred shares, shares issued		0
Treasury shares reissued during the year		0	0	0
Officers and Directors
Common Shares
Restricted stock awarded to executive officers, key employees & directors		3,530,033	1,926,861	4,847,376
Restricted shares awarded, average market price (in dollars per share)		$ 10.09	$ 19.53	$ 16.28
Employees
Common Shares
Issuance of common shares for stock options exercised, net of surrender of unexercised stock options (in shares)				1,284