Income Taxes - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Mar. 31, 2015
Income Tax Contingency [Line Items]
Effective income tax rate	45.60%	46.70%	44.00%	46.50%
Effective income tax rate decrease during period	(6.50%)
Concentra Inc.
Income Tax Contingency [Line Items]
Effective income tax rate decrease during period			(6.50%)
Deferred tax asset					$ 53