Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Assets
Fixed maturities, trading securities, at fair value (amortized cost: 2011, $13,394,404; 2010, $12,394,797)	$ 13,941,829	$ 12,824,389
Short-term investments, trading securities, at fair value (amortized cost: 2011, $42,563; 2010, $49,132)	42,571	49,397
Equities, trading securities, at fair value (cost: 2011, $917,613; 2010, $942,745)	944,691	1,071,676
Other invested assets	358,154	352,405
Total investments	15,287,245	14,297,867
Funds held - directly managed (cost: 2011, $1,241,222; 2010, $1,751,276)	1,268,010	1,772,118
Cash and cash equivalents, at fair value, which approximates amortized cost	1,342,257	2,111,084
Accrued investment income	189,074	201,928
Reinsurance balances receivable	2,059,976	2,076,884
Reinsurance recoverable on paid and unpaid losses	397,788	382,878
Funds held by reinsured companies	796,290	937,032
Deferred acquisition costs	547,202	595,557
Deposit assets	241,513	256,702
Net tax assets	66,574	14,960
Goodwill	455,533	455,533
Intangible assets	133,867	178,715
Other assets	70,044	83,113
Total assets	22,855,373	23,364,371
Liabilities
Unpaid losses and loss expenses	11,273,091	10,666,604
Policy benefits for life and annuity contracts	1,645,662	1,750,410
Unearned premiums	1,448,841	1,599,139
Other reinsurance balances payable	443,873	491,194
Deposit liabilities	249,382	268,239
Net tax liabilities	297,153	316,325
Accounts payable, accrued expenses and other	208,840	244,552
Debt related to senior notes	750,000	750,000
Debt related to capital efficient notes	70,989	70,989
Total liabilities	16,387,831	16,157,452
Shareholders' Equity
Common shares (par value $1.00, issued: 2011, 84,766,693 shares; 2010, 84,033,089 shares)	84,767	84,033
Preferred shares (par value $1.00; issued and outstanding: 2011, 35,750,000 shares; 2010, 20,800,000 shares; aggregate liquidation value: 2011, $893,750; 2010, $520,000)	35,750	20,800
Additional paid-in capital	3,803,796	3,419,864
Accumulated other comprehensive (loss) income:
Currency translation adjustment	4,267	16,101
Other accumulated comprehensive (loss) income (net of tax of: 2011, $6,590; 2010, $4,872)	(16,911)	(12,045)
Retained earnings	4,035,103	4,761,178
Common shares held in treasury, at cost (2011, 19,444,365 shares; 2010, 14,046,895 shares)	(1,479,230)	(1,083,012)
Total shareholders' equity	6,467,542	7,206,919
Total liabilities and shareholders' equity	$ 22,855,373	$ 23,364,371