Fair Value Measurements (Quantitative Information About Level 3 Fair Value Measurements) (Details) (USD $)	3 Months Ended	12 Months Ended
	Mar. 31, 2013	Dec. 31, 2012
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Goodwill	565,886,000	565,886,000
Lease impairment obligation		7,400,000
Western Region Operations [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Goodwill	565,900,000	565,900,000
Level 3 [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Lease impairment obligation		7,400,000
Level 3 [Member] | Monte Carlo Simulation Approach [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Embedded contractual derivative asset	10,900,000	11,200,000
Embedded contractual derivative liability	4,200,000	3,200,000
Level 3 [Member] | Income Approach [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Lease impairment obligation		7,400,000
Level 3 [Member] | Western Region Operations [Member] | Income Approach [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Goodwill		565,900,000
Level 3 [Member] | Embedded contractual derivative asset [Member] | Monte Carlo Simulation Approach [Member] | Health Net Health Care Expenditures [Member] | Minimum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Health Care Expenditures, range (as a percentage)	(0.20%)	(1.70%)
Level 3 [Member] | Embedded contractual derivative asset [Member] | Monte Carlo Simulation Approach [Member] | Health Net Health Care Expenditures [Member] | Maximum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Health Care Expenditures, range (as a percentage)	(0.20%)	0.80%
Level 3 [Member] | Embedded contractual derivative asset [Member] | Monte Carlo Simulation Approach [Member] | Health Net Health Care Expenditures [Member] | Weighted Average [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Health Care Expenditures, range (as a percentage)	(0.20%)	(0.40%)
Level 3 [Member] | Embedded contractual derivative asset [Member] | Monte Carlo Simulation Approach [Member] | National Health Care Expenditures [Member] | Minimum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Health Care Expenditures, range (as a percentage)	3.70%	3.70%
Level 3 [Member] | Embedded contractual derivative asset [Member] | Monte Carlo Simulation Approach [Member] | National Health Care Expenditures [Member] | Maximum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Health Care Expenditures, range (as a percentage)	3.70%	3.70%
Level 3 [Member] | Embedded contractual derivative asset [Member] | Monte Carlo Simulation Approach [Member] | National Health Care Expenditures [Member] | Weighted Average [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Health Care Expenditures, range (as a percentage)	3.70%	3.70%
Level 3 [Member] | Embedded contractual derivative liability [Member] | Monte Carlo Simulation Approach [Member] | Health Net Health Care Expenditures [Member] | Minimum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Health Care Expenditures, range (as a percentage)	1.10%	(0.30%)
Level 3 [Member] | Embedded contractual derivative liability [Member] | Monte Carlo Simulation Approach [Member] | Health Net Health Care Expenditures [Member] | Maximum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Health Care Expenditures, range (as a percentage)	9.10%	10.10%
Level 3 [Member] | Embedded contractual derivative liability [Member] | Monte Carlo Simulation Approach [Member] | Health Net Health Care Expenditures [Member] | Weighted Average [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Health Care Expenditures, range (as a percentage)	4.90%	4.90%
Level 3 [Member] | Embedded contractual derivative liability [Member] | Monte Carlo Simulation Approach [Member] | National Health Care Expenditures [Member] | Minimum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Health Care Expenditures, range (as a percentage)	(0.30%)	(0.10%)
Level 3 [Member] | Embedded contractual derivative liability [Member] | Monte Carlo Simulation Approach [Member] | National Health Care Expenditures [Member] | Maximum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Health Care Expenditures, range (as a percentage)	7.40%	7.30%
Level 3 [Member] | Embedded contractual derivative liability [Member] | Monte Carlo Simulation Approach [Member] | National Health Care Expenditures [Member] | Weighted Average [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Health Care Expenditures, range (as a percentage)	3.40%	3.30%
Level 3 [Member] | Goodwill [Member] | Western Region Operations [Member] | Income Approach [Member] | Minimum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount Rate, range (as a percentage)		9.00%
Level 3 [Member] | Goodwill [Member] | Western Region Operations [Member] | Income Approach [Member] | Maximum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount Rate, range (as a percentage)		9.00%
Level 3 [Member] | Goodwill [Member] | Western Region Operations [Member] | Income Approach [Member] | Weighted Average [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount Rate, range (as a percentage)		9.00%
Level 3 [Member] | Liability [Member] | Income Approach [Member] | Minimum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount Rate, range (as a percentage)		3.26%
Level 3 [Member] | Liability [Member] | Income Approach [Member] | Maximum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount Rate, range (as a percentage)		3.26%
Level 3 [Member] | Liability [Member] | Income Approach [Member] | Weighted Average [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount Rate, range (as a percentage)		3.26%