CONSOLIDATED BALANCE SHEETS (Unaudited) (Parenthetical) (USD $) In Thousands, except Per Share data, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Securities, available-for-sale, at fair value:
Fixed maturities, amortized cost	$ 4,506,873	$ 4,185,937
Shareholders' equity (note 14):
Common stock, par value (in dollars per share)	$ 1	$ 1
Common stock, shares authorized (in shares)	680,000	680,000
Common stock, shares issued (in shares)	340,047	205,047
Common stock, shares outstanding (in shares)	337,758	202,032
Treasury stock, shares at cost (in shares)	2,289	3,015