Investments Contractual Maturities of Investments (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Cost
Due in one year or less	$ 524,663
Due after one year through five years	102,182
Amortized Cost	626,845
Preferred stock	3,270
Amortized Cost	630,115	149,097
Fair Value
Due in one year or less	524,814
Due after one year through five years	100,241
Fair Value	625,055
Preferred stock	3,487
Fair Value	$ 628,542	$ 146,972