Liability for Unpaid Claims - Summary of Liability for Unpaid Health Claims (Details) - Health Insurance [Member] - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Activity in the Liability for Unpaid Health Claims
Balance at beginning of period	$ 146,865	$ 143,128
Incurred related to:
Current year	134,542	135,377
Prior years	(5,001)	(4,024)
Total incurred	129,541	131,353
Paid related to:
Current year	55,130	54,241
Prior years	78,722	77,555
Total paid	133,852	131,796
Balance at end of period	$ 142,554	$ 142,685