Components of Changes in Medical Payables (Detail) $ in Thousands	3 Months Ended
	Mar. 31, 2017 USD ($)
Health Care Costs Payable [Roll Forward]
Health care costs payable, beginning of the period	$ 336,381
Less: Claims paid
Health care costs payable, end of the period	389,681
Healthcare Cost
Health Care Costs Payable [Roll Forward]
Health care costs payable, beginning of the period	214,275
Add: Components of incurred health care costs
Current year	467,683
Prior years	421
Total incurred health care costs	468,104
Less: Claims paid
Current year	247,723
Prior years	172,693
Total claims paid	420,416
Health care costs payable, end of the period	$ 261,963