Significant Accounting Policies (Medicare Part D) (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Summary of Significant Accounting Policies [Abstract]
Reimbursed amount of catastrophic reinsurance subsidy	80.00%
Catastrophic reinsurance subsidy	$ 4,700	$ 4,550	$ 4,550
Medicare coverage gap discount	50.00%
Premiums subject to risk corridor provisions variance	5.00%