Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Assets
Fixed maturities, at amortized cost	$ 5,556,900	$ 5,546,994
Short-term investments, at amortized cost	1,941,615	1,501,360
Other investments, at amortized cost	315,963	320,476
Investments in and advance to affiliates, subsidiaries, associates, and joint ventures, at cost	$ 70,186	$ 107,501
Shareholders' equity
Common shares, shares authorized	571,428,571	571,428,571
Common shares, par value	$ 0.175	$ 0.175
Common shares, shares issued	160,570,772	155,554,224
Common shares, shares outstanding	82,900,617	83,869,845
Treasury stock, common shares	77,670,155	71,684,379