Fair Value Measurements (Quantitative Information About Level 3 Fair Value Measurements) (Details) (USD $)	9 Months Ended	12 Months Ended
	Sep. 30, 2013	Dec. 31, 2012
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Goodwill	$ 565,886,000	$ 565,886,000
Western Region Operations [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Goodwill	565,900,000	565,900,000
Level 3 [Member] | Monte Carlo Simulation Approach [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Embedded contractual derivative asset	12,700,000	11,200,000
Embedded contractual derivative liability	700,000	3,200,000
Level 3 [Member] | Income Approach [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Lease impairment obligation		7,400,000
State-sponsored health plans settlement account deficit	51,700,000
Level 3 [Member] | Western Region Operations [Member] | Income Approach [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Goodwill	$ 565,900,000	$ 565,900,000
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)	10.00%	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)	10.00%	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)	10.00%	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%
Embedded contractual derivative liability [Member] | Level 3 [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)	2.59%	(0.30%)
Embedded contractual derivative liability [Member] | Level 3 [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)	6.10%	10.10%
Embedded contractual derivative liability [Member] | Level 3 [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)	4.26%	4.90%
Embedded contractual derivative liability [Member] | Level 3 [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)	(1.80%)	(0.10%)
Embedded contractual derivative liability [Member] | Level 3 [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)	8.85%	7.30%
Embedded contractual derivative liability [Member] | Level 3 [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)	4.00%	3.30%
Embedded Contractual Derivative Asset [Member] | Level 3 [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)	(5.34%)	(1.70%)
Embedded Contractual Derivative Asset [Member] | Level 3 [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)	7.91%	0.80%
Embedded Contractual Derivative Asset [Member] | Level 3 [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)	0.69%	(0.40%)
Embedded Contractual Derivative Asset [Member] | Level 3 [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)	(0.55%)	3.70%
Embedded Contractual Derivative Asset [Member] | Level 3 [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)	7.04%	3.70%
Embedded Contractual Derivative Asset [Member] | Level 3 [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)	3.35%	3.70%
State-sponsored health plans settlement account deficit [Member] | Level 3 [Member] | Income Approach [Member] | Minimum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount Rate, range (as a percentage)	1.135%
State-sponsored health plans settlement account deficit [Member] | Level 3 [Member] | Income Approach [Member] | Maximum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount Rate, range (as a percentage)	1.135%
State-sponsored health plans settlement account deficit [Member] | Level 3 [Member] | Income Approach [Member] | Weighted Average [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount Rate, range (as a percentage)	1.135%