Unaudited Condensed Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Assets
Fixed maturities, trading securities, at fair value (amortized cost: 2012, $13,811,342; 2011, $13,394,404)	$ 14,411,664	$ 13,941,829
Short-term investments, trading securities, at fair value (amortized cost: 2012, $38,819; 2011, $42,563)	38,838	42,571
Equities, trading securities, at fair value (cost: 2012, $865,452; 2011, $917,613)	943,458	944,691
Other invested assets	360,894	358,154
Total investments	15,754,854	15,287,245
Funds held - directly managed (cost: 2012, $1,230,199; 2011, $1,241,222)	1,264,383	1,268,010
Cash and cash equivalents, at fair value, which approximates amortized cost	1,210,229	1,342,257
Accrued investment income	181,898	189,074
Reinsurance balances receivable	2,571,038	2,059,976
Reinsurance recoverable on paid and unpaid losses	432,059	397,788
Funds held by reinsured companies	799,988	796,290
Deferred acquisition costs	636,537	547,202
Deposit assets	242,435	241,513
Net tax assets	44,769	66,574
Goodwill	455,533	455,533
Intangible assets	124,974	133,867
Other assets	76,959	70,044
Total assets	23,795,656	22,855,373
Liabilities
Unpaid losses and loss expenses	11,143,354	11,273,091
Policy benefits for life and annuity contracts	1,707,982	1,645,662
Unearned premiums	2,017,177	1,448,841
Other reinsurance balances payable	522,701	443,873
Deposit liabilities	249,967	249,382
Net tax liabilities	311,069	297,153
Accounts payable, accrued expenses and other	235,546	208,840
Debt related to senior notes	750,000	750,000
Debt related to capital efficient notes	70,989	70,989
Total liabilities	17,008,785	16,387,831
Shareholders' Equity
Common shares (par value $1.00, issued: 2012, 84,939,858 shares; 2011, 84,766,693 shares)	84,940	84,767
Preferred shares (par value $1.00; issued and outstanding: 2012 and 2011, 35,750,000 shares; aggregate liquidation value: 2012 and 2011, $893,750)	35,750	35,750
Additional paid-in capital	3,815,056	3,803,796
Accumulated other comprehensive income (loss):
Currency translation adjustment	21,474	4,267
Other accumulated comprehensive loss (net of tax of: 2012, $6,780; 2011, $6,590)	(18,022)	(16,911)
Retained earnings	4,339,296	4,035,103
Common shares held in treasury, at cost (2012, 19,626,865 shares; 2011, 19,444,365 shares)	(1,491,623)	(1,479,230)
Total shareholders' equity	6,786,871	6,467,542
Total liabilities and shareholders' equity	$ 23,795,656	$ 22,855,373