Fair Value Measurements (Quantitative Information about Level 3 Fair Value Measurements) (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Goodwill	558,886,000	565,886,000	$ 565,900,000
Western Region Operations [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Goodwill	558,900,000	565,900,000	565,900,000
Level 3 [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Assets held for sale	50,000,000
Level 3 [Member] | Monte Carlo Simulation Approach [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Embedded contractual derivative asset	10,000,000	7,200,000
Embedded contractual derivative liability	2,600,000
Level 3 [Member] | Income Approach [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
State-sponsored health plans settlement account deficit		62,900,000
Assets held for sale	50,000,000
Level 3 [Member] | Income Approach [Member] | Western Region Operations [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Goodwill	558,900,000	565,900,000
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)	(0.08%)	(3.34%)
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)	2.74%	7.34%
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)	2.02%	2.20%
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)	3.45%	(0.77%)
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)	4.14%	9.46%
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)	3.80%	3.63%
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)	0.79%
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)	10.76%
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)	5.73%
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)	0.64%
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)	8.43%
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)	4.38%
Goodwill [Member] | Level 3 [Member] | Income Approach [Member] | Western Region Operations [Member] | Minimum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount Rate, range (as a percentage)	7.50%	10.00%
Goodwill [Member] | Level 3 [Member] | Income Approach [Member] | Western Region Operations [Member] | Maximum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount Rate, range (as a percentage)	7.50%	10.00%
Goodwill [Member] | Level 3 [Member] | Income Approach [Member] | Western Region Operations [Member] | Weighted Average [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount Rate, range (as a percentage)	7.50%	10.00%
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%
Assets Held-for-sale [Member] | Level 3 [Member] | Income Approach [Member] | Minimum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount Rate, range (as a percentage)	12.00%
Assets Held-for-sale [Member] | Level 3 [Member] | Income Approach [Member] | Maximum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount Rate, range (as a percentage)	12.00%
Assets Held-for-sale [Member] | Level 3 [Member] | Income Approach [Member] | Weighted Average [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Discount Rate, range (as a percentage)	12.00%
Recurring [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Embedded contractual derivative asset	10,000,000	7,200,000
State-sponsored health plans settlement account deficit	0	62,900,000
Recurring [Member] | Level 3 [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Embedded contractual derivative asset	10,000,000	7,200,000
State-sponsored health plans settlement account deficit	0	62,900,000
Embedded contractual derivative liability	2,600,000