Estimated Cost of Providing Uncompensated Care (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Health Care Trust Fund [Line Items]
Estimated cost of providing uncompensated care	$ 239,620	$ 213,807	$ 184,187
Charity Care
Health Care Trust Fund [Line Items]
Estimated cost of providing uncompensated care	120,208	107,887	77,557
Uninsured Discounts
Health Care Trust Fund [Line Items]
Estimated cost of providing uncompensated care	$ 119,412	$ 105,920	$ 106,630