Business Segment Information - Identifiable Assets by Business Segment (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment reporting information
Restricted cash	$ 229,013	$ 81,776	$ 133,597
Net accounts receivable	660,775	606,764	428,644
Investments	327,865	305,253	326,165
Pharmaceutical inventory	40,945	58,995	50,749
Goodwill	1,006,288	742,054	621,390
Other intangible assets, net	268,288	186,232	133,374
Operating segments | Healthcare
Segment reporting information
Restricted cash	220,786	81,608	133,597
Net accounts receivable	244,486	191,058	153,036
Investments	327,865	293,034	313,045
Goodwill	610,867	350,576	260,618
Other intangible assets, net	165,159	55,756	12,227
Operating segments | Pharmacy Management
Segment reporting information
Restricted cash	8,059	1
Net accounts receivable	403,880	405,611	270,975
Investments		10,703
Pharmaceutical inventory	40,945	58,995	50,749
Goodwill	395,421	391,478	360,772
Other intangible assets, net	103,129	130,476	121,147
Corporate and Elimination
Segment reporting information
Restricted cash	168	167
Net accounts receivable	$ 12,409	10,095	4,633
Investments		$ 1,516	$ 13,120