Credit Facilities (Narrative) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Dec. 31, 2012	Aug. 23, 2006
Line of Credit Facility [Line Items]
Line of credit facility, commitment	$ 150,000	$ 150,000
Line of credit facility, description of variable rate basis	the rate of interest publicly announced by Citibank as its base rate
Total Citibank Holdings Credit Facility [Member]
Line of Credit Facility [Line Items]
Line of credit facility, term of credit facility	3 years		5 years
Line of credit facility, commitment	150,000	150,000
Line of credit facility, required minimum debt-to-capital ratio	0.35
Line of credit facility, required minimum net worth	1,875,000
Percentage amount of consolidated net income required to be reserved to maintain compliance with facility covenants	25.00%
Percentage amount of increase in consolidated net worth from new issuance required to be reserved to maintain compliance with facility covenants	25.00%
Increase in reserves due to new issuance during the period required to maintain compliance with facility covenants	$ 2,016,650
Total Citibank Holdings Credit Facility [Member] | Interest Rate Base Rate Option 1(b) [Member]
Line of Credit Facility [Line Items]
Line of credit facility, spread on variable rate basis	0.50%
Total Citibank Holdings Credit Facility [Member] | Interest Rate Base Rate Option 1(c) [Member]
Line of Credit Facility [Line Items]
Line of credit facility, description of variable rate basis	% above the one month London Interbank Offered Rate ("LIBOR"), in each case plus the applicable margin
Line of credit facility, spread on variable rate basis	1.00%
Total Citibank Holdings Credit Facility [Member] | Interest Rate Base Rate Option 2 [Member]
Line of Credit Facility [Line Items]
Line of credit facility, description of variable rate basis	periodic fixed rate equal to the Eurodollar Rate plus an applicable margin