Investments (Details 4) (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2011	Jun. 30, 2012	Dec. 31, 2011
Cumulative credit loss (1)
Beginning of period	$ 4,518	$ 3,957	$ 3,957
Losses related to securities sold or paid down during the period	(561)
End of period	$ 3,957	$ 3,957	$ 3,957