Condensed Consolidated Balance Sheets (Unaudited) (Parenthetical) (USD $) In Thousands, except Share data	Jun. 30, 2011	Dec. 31, 2010
Share capital
Common shares, par value	$ 1	$ 1
Common shares, authorized	156,000,000	156,000,000
SHAREHOLDERS' EQUITY - Share capital - Authorized, issued and fully paid, par value $1 each (authorized 2011: 156,000,000; 2010: 156,000,000)
Treasury shares at cost (Series A non-voting convertible ordinary shares)	2,972,892	2,972,892
Short-term Investments
ASSETS
Short-term investments, available-for-sale, at amortized cost	$ 0	$ 7,209
Fixed Maturities
ASSETS
Short-term investments, available-for-sale, at amortized cost	$ 817,284	$ 1,068,540
Share Capital - Ordinary Shares
SHAREHOLDERS' EQUITY - Share capital - Authorized, issued and fully paid, par value $1 each (authorized 2011: 156,000,000; 2010: 156,000,000)
Ordinary shares, issued	13,519,723	12,940,021
Ordinary shares, outstanding	13,519,723	12,940,021
Series A Common Stock
SHAREHOLDERS' EQUITY - Share capital - Authorized, issued and fully paid, par value $1 each (authorized 2011: 156,000,000; 2010: 156,000,000)
Ordinary shares, issued	2,972,892	2,972,892
Series B, C and D Common Stock
SHAREHOLDERS' EQUITY - Share capital - Authorized, issued and fully paid, par value $1 each (authorized 2011: 156,000,000; 2010: 156,000,000)
Ordinary shares, issued	749,869	0
Ordinary shares, outstanding	749,869	0