Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
ASSETS
Investments collateralizing repurchase agreements	$ 416,771	$ 432,768
Investments in associated companies (measured using fair value option)	$ 1,566,553	$ 1,198,029
EQUITY
Common shares, par value	$ 1	$ 1
Common shares, authorized (actual number)	600,000,000	600,000,000
Common shares, issued and outstanding after deducting shares held in treasury (actual number)	244,582,588	244,582,588
Treasury stock, shares (actual number)	47,006,711	47,006,711