Liability for Unpaid Claims - Summary of Liability for Unpaid Health Claims (Details) - Health Insurance [Member] - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Activity in the Liability for Unpaid Health Claims
Balance at beginning of period	$ 146,865	$ 143,128
Incurred related to:
Current year	269,574	264,648
Prior years	(5,708)	(8,364)
Total incurred	263,866	256,284
Paid related to:
Current year	171,199	164,271
Prior years	99,054	94,676
Total paid	270,253	258,947
Balance at end of period	$ 140,478	$ 140,465