Consolidated Balance Sheets (Parentheticals) (USD $) In Thousands, except Share data, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Balance Sheet Parenthetical Disclosure Assets
Fixed maturities, trading securities, amortized cost	$ 13,653,615	$ 13,394,404
Short-term investments, trading securities, amortized cost	150,634	42,563
Equities, trading securities, cost	1,000,326	917,613
Funds held - directly managed, cost	895,261	1,241,222
Balance Sheet Parenthetical Disclosures Equity
Common shares, par value	$ 1	$ 1
Common shares, shares issued	85,459,905	84,766,693
Common shares held in treasury, shares	26,550,530	19,444,365
Preferred shares, par value	$ 1	$ 1
Preferred shares, shares issued	35,750,000	35,750,000
Preferred shares, shares outstanding	35,750,000	35,750,000
Aggregate liquidation value	$ 893,750	$ 893,750