Investments Contractual Maturities of Investments (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Cost
Due in one year or less	$ 484,771
Due after one year through five years	101,210
Amortized Cost	585,981
Preferred stock	13,513
Amortized Cost	599,494	149,097
Fair Value
Due in one year or less	484,906
Due after one year through five years	97,384
Fair Value	582,290
Preferred stock	13,724
Fair Value	$ 596,014	$ 146,972