Business Segment Information - Changes Related to Allocation of Corporate Operational Support Functions (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Summary of changes by business segment
Segment profit (loss) before Corporate allocations	$ 301,793	$ 275,651	$ 266,919
Segment profit (loss)	301,793	275,651	266,919
Operating segments | Healthcare
Summary of changes by business segment
Segment profit (loss) before Corporate allocations	282,421	250,069	278,485
Allocated Corporate costs	(74,498)	(72,792)	(65,296)
Allocated Corporate stock compensation expense	5,018	5,946	3,755
Segment profit (loss)	212,941	183,223	216,944
Operating segments | Pharmacy Management
Summary of changes by business segment
Segment profit (loss) before Corporate allocations	140,625	135,820	101,110
Allocated Corporate costs	(19,150)	(19,307)	(17,365)
Allocated Corporate stock compensation expense	1,254	1,487	938
Segment profit (loss)	122,729	118,000	84,683
Corporate and Elimination
Summary of changes by business segment
Segment profit (loss) before Corporate allocations	(121,253)	(110,238)	(112,676)
Allocated Corporate costs	93,648	92,099	82,661
Allocated Corporate stock compensation expense	(6,272)	(7,433)	(4,693)
Segment profit (loss)	$ (33,877)	$ (25,572)	$ (34,708)