Significant Accounting Policies (Details 3) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Health Care Organization, Expenses, Gross [Abstract]
Fee-for-service	$ 3,521,960,000	$ 2,764,309,000	$ 2,360,858,000
Capitation	557,087,000	518,835,000	555,487,000
Pharmacy	835,830,000	418,007,000	325,935,000
Other	181,883,000	158,843,000	128,577,000
Total	5,096,760,000	3,859,994,000	3,370,857,000
Percentage of total in Fee for service	69.10%	71.60%	70.00%
Percentage of total in capitation	10.90%	13.40%	16.50%
Percentage of total in pharmacy	16.40%	10.80%	9.70%
Percentage of total in other	3.60%	4.20%	3.80%
Percentage of total	100.00%	100.00%	100.00%
PMPM [Member]
Health Care Organization, Expenses, Gross [Abstract]
Fee-for-service	162.60	139.02	128.73
Capitation	25.72	26.09	30.29
Pharmacy	38.59	21.02	17.77
Other	8.39	8.00	7.01
Total	$ 235.30	$ 194.13	$ 183.80