Consolidated Balance Sheets (Parentheticals) (USD $) In Thousands, except Share data, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Balance Sheet Parenthetical Disclosure Assets
Fixed maturities, trading securities, amortized cost	$ 13,394,404	$ 12,394,797
Short-term investments, trading securities, amortized cost	42,563	49,132
Equities, trading securities, cost	917,613	942,745
Funds held - directly managed, cost	1,241,222	1,751,276
Balance Sheet Parenthetical Disclosures Equity
Common shares, par value	$ 1	$ 1
Common shares, shares issued	84,766,693	84,033,089
Other accumulated comprehensive (loss) income, tax	6,590	4,872
Common shares held in treasury, shares	19,444,365	14,046,895
Shareholders' Equity [Line Items]
Preferred shares, par value	$ 1	$ 1
Preferred shares, shares issued	35,750,000	20,800,000
Preferred shares, shares outstanding	35,750,000	20,800,000
Aggregate liquidation value	$ 893,750	$ 520,000