Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Consolidated Balance Sheets
Fixed maturity securities, available-for-sale, amortized cost (in dollars)	$ 9,659,413	$ 9,638,404
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized	500,000,000	500,000,000
Common stock, shares issued	182,524,573	182,235,798
Common stock, shares outstanding	182,524,573	182,235,798
Accumulated other comprehensive income, tax provision (in dollars)	$ 149,205	$ 135,344
Deferred equity compensation, shares	320,193	320,193