Significant Accounting Policies (Government Contracts) (Details) (USD $)	12 Months Ended				12 Months Ended						12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Mar. 31, 2011 Government Contracts [Member] options	Dec. 31, 2012 Government Contracts [Member] TRICARE Contract North Region [Member]	Dec. 31, 2011 Government Contracts [Member] TRICARE Contract North Region [Member]	Dec. 31, 2010 Government Contracts [Member] TRICARE Contract North Region [Member]	Dec. 31, 2012 Government Contracts [Member] T-3 Contract [Member]	Dec. 31, 2011 Government Contracts [Member] T-3 Contract [Member]	Apr. 02, 2011 Government Contracts [Member] T-3 Contract [Member]	Dec. 31, 2012 Government Contracts [Member] MFLC Contract [Member]	Dec. 31, 2011 Government Contracts [Member] MFLC Contract [Member]	Dec. 31, 2010 Government Contracts [Member] MFLC Contract [Member]
Significant Accounting Policies [Line Items]
Number of administrative services option periods				5
Deferred costs										$ 43,800,000
Effective date of contract									April 1, 2011		August 15, 2012
Administrative services option period											5 years
Deferred revenue	0	0								52,500,000
Costs paid and reimbursable								2,600,000,000	1,700,000,000
Percentage of reimbursed health care target costs and underwriting fees					80.00%
Percentage of unreimbursed health care target costs and underwriting fees					20.00%
Changes in estimate of target cost revenues						(42,000,000)	(51,000,000)
Changes in estimated of target costs						(52,000,000)	(64,000,000)
Contracts revenue	$ 689,121,000	$ 1,416,619,000	$ 3,344,483,000								$ 221,000,000	$ 259,000,000	$ 275,000,000