CONSOLIDATED BALANCE SHEETS (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
CONSOLIDATED BALANCE SHEETS
Available for sale, amortized cost (in dollars)	$ 1,305,903	$ 978,502
Statement
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized	10,000,000	10,000,000
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized	100,000,000	100,000,000
Common stock, shares issued	83,958,844	83,487,340
Common stock, shares outstanding	83,958,844	83,487,340
Series B Preferred Stock
Statement
Preferred stock, liquidation value per share (in dollars per share)	$ 1,000	$ 1,000
Preferred stock, shares issued	114,068	114,068
Preferred stock, shares outstanding	114,068	114,068