Income Taxes - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Mar. 31, 2015
Income Tax Contingency [Line Items]
Effective income tax rate	51.50%	47.50%	46.20%	46.80%
Effective income tax rate decrease during period	(4.60%)
Concentra Inc.
Income Tax Contingency [Line Items]
Effective income tax rate decrease during period			(4.60%)
Deferred tax asset					$ 53