Bank Line of Credit (Details) (Revolving line of credit, USD $) In Millions, unless otherwise specified	1 Months Ended	9 Months Ended
	Oct. 25, 2013	Sep. 30, 2013
Indemnity
Bank Line of Credit
Maximum borrowing capacity under the bank revolving line of credit		$ 100
Maximum letter of credit sublimit under the bank revolving line of credit		25
Expiration date of the bank revolving line of credit		Nov. 03, 2016
Available borrowing capacity under the bank revolving line of credit, due to outstanding letters of credit		98.2
Outstanding amount of letters of credit sublimit under the bank revolving line of credit		1.8
Available amount of letters of credit sublimit under the bank revolving line of credit		23.2
Borrowings outstanding under the bank revolving line of credit		0
Fair value of bonds pledged as collateral on the bank revolving line of credit		111
Exchange
Bank Line of Credit
Maximum borrowing capacity under the bank revolving line of credit		300
Maximum letter of credit sublimit under the bank revolving line of credit		25
Expiration date of the bank revolving line of credit		Oct. 28, 2016
Available borrowing capacity under the bank revolving line of credit, due to outstanding letters of credit		298.9
Outstanding amount of letters of credit sublimit under the bank revolving line of credit		1.1
Available amount of letters of credit sublimit under the bank revolving line of credit		23.9
Borrowings outstanding under the bank revolving line of credit		0
Fair value of bonds pledged as collateral on the bank revolving line of credit		$ 332
Subsequent event | Indemnity
Bank Line of Credit
Expiration date of the bank revolving line of credit	Nov. 03, 2018
Subsequent event description		On October 25, 2013, Indemnity amended its revolving credit facility to extend the maturity date to November 3, 2018, lower the borrowing costs, and eliminate the minimum net worth financial covenant.
Subsequent event | Exchange
Bank Line of Credit
Expiration date of the bank revolving line of credit	Oct. 25, 2018
Subsequent event description		On October 25, 2013, the Exchange entered into a second amended and restated credit agreement to extend the maturity date to October 25, 2018, lower the borrowing costs, and eliminate the minimum statutory surplus covenant.