Fair Value Measurements (Quantitative Information About Level 3 Fair Value Measurements) (Details) (USD $)	3 Months Ended	12 Months Ended
	Mar. 31, 2014	Dec. 31, 2013
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	11,400,000	7,200,000
Level 3 [Member] | Income Approach [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
State-sponsored health plans settlement account deficit	50,000,000	62,900,000
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
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)	(3.09%)	(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)	4.36%	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)	1.59%	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)	0.26%	(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)	6.60%	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)	3.63%	3.63%
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%	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%	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%	1.135%
Goodwill [Member] | Level 3 [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%	10.00%
Goodwill [Member] | Level 3 [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%	10.00%
Goodwill [Member] | Level 3 [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%	10.00%