Income Taxes (Reconciliation) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended	12 Months Ended	1 Months Ended
Sep. 30, 2014	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Sep. 30, 2014
Statutory federal income tax rate		35.00%	35.00%	35.00%
State and local taxes, net of federal income tax effect		(11.10%)	1.50%	(6.90%)
Valuation allowance (release) against capital losses, net operating losses or tax credits		0.00%	0.00%	(26.50%)
Loss on Subsidiary Stock		(24.90%)	0.00%	0.00%
Non-deductible health insurer fee		24.80%	0.00%	0.00%
Non-deductible compensation		4.80%	3.60%	17.70%
Tax exempt interest income		(2.90%)	(2.40%)	(12.70%)
Sale of subsidiaries		0.00%	0.00%	1.80%
Interest expense		(1.00%)	(0.10%)	5.30%
Lobbying expense		0.60%	0.40%	3.40%
Other, net		1.80%	(1.00%)	1.80%
Effective income tax rate		27.10%	37.00%	18.90%
Tax Benefit Due to Worthless Stock loss	$ 72.6hnt_TaxBenefitDuetoWorthlessStockloss	$ 73.7hnt_TaxBenefitDuetoWorthlessStockloss
Unrecognized Tax Benefits, Increase Resulting from Current Period Tax Positions		25.5	4.4	2.4
Unrecognized Tax Benefits, Decrease Resulting from Current Period Tax Positions		16.4
ACA Health Insurer Fee [Member]
ACA Health Insurer Fee Payment		$ 141.4			$ 141.4

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Percentage of domestic federal statutory tax rate applicable to pretax income (loss).

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Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to other deductions.

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Amount of increase in unrecognized tax benefits resulting from tax positions that have been or will be taken in current period tax return.

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