Investments Investments in Any One Issuer Exceeding Ten Percent of Equity (Details) (USD $) In Thousands, unless otherwise specified				12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2013 Credit Concentration Risk [Member]	Dec. 31, 2013 Stockholders' Equity, Total [Member]	Dec. 31, 2013 Government National Mortgage Association Certificates and Obligations (GNMA) [Member] Credit Concentration Risk [Member]	Dec. 31, 2013 Federal Home Loan Mortgage Corporation Certificates and Obligations (FHLMC) [Member] Credit Concentration Risk [Member]	Dec. 31, 2013 Federal National Mortgage Association Certificates and Obligations (FNMA) [Member] Credit Concentration Risk [Member]
Concentration Risk [Line Items]
Concentration Risk, Percentage				10.00%
Available-for-sale Securities, Amortized Cost Basis	$ 694,832	$ 690,556	$ 515,730		$ 293,580	$ 111,483	$ 110,667
Available-for-sale Securities	$ 691,729	$ 699,300	$ 511,952		$ 289,497	$ 111,617	$ 110,838