Acquisitions - 4D Pharmacy Management Systems (Details) - USD ($) $ in Thousands		12 Months Ended
	Apr. 01, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Assets acquired:
Goodwill		$ 621,390	$ 566,106	$ 488,206
Acquisition disclosures
Changes in fair value: Increase (Decrease) in contingent consideration		44,257	9,304
Payment on contingent consideration		29,274
Fair value of the short term contingent consideration		91,623	$ 8,314
4D Pharmacy Management Systems, Inc.
Acquisitions
Amount of consideration paid in cash	$ 55,000
Assets acquired:
Current assets	35,638
Property and equipment, net	238
Other identified intangible assets	24,600
Goodwill	49,136
Total assets acquired	109,612
Liabilities assumed:
Current liabilities	33,882
Contingent consideration	19,291
Total liabilities assumed	53,173
Net assets acquired	56,439
Acquisition disclosures
Maximum potential contingent payments	30,000
Working capital payable		200
Estimated undiscounted future contingent payments	20,600	1,000
Net increase or decrease in contingent consideration liability		(19,600)
Changes in fair value: Increase (Decrease) in contingent consideration		(600)
Payment on contingent consideration		19,000
Fair value of the short term contingent consideration		1,000
Acquisition related costs		200
Cumulative acquisition related costs		$ 700
4D Pharmacy Management Systems, Inc. | Cash
Assets acquired:
Current assets	14,178
4D Pharmacy Management Systems, Inc. | Accounts receivable
Assets acquired:
Current assets	21,417
4D Pharmacy Management Systems, Inc. | Customer contracts
Assets acquired:
Other identified intangible assets	$ 21,100
Acquisition disclosures
Period of amortization of intangible assets acquired	10 years
4D Pharmacy Management Systems, Inc. | Non-compete agreements
Assets acquired:
Other identified intangible assets	$ 2,200
Acquisition disclosures
Period of amortization of intangible assets acquired	5 years
4D Pharmacy Management Systems, Inc. | Tradenames
Assets acquired:
Other identified intangible assets	$ 1,300
Acquisition disclosures
Period of amortization of intangible assets acquired	18 months
4D Pharmacy Management Systems, Inc. | Achievement Of Certain Targets
Acquisition disclosures
Maximum potential contingent payments	$ 10,000
4D Pharmacy Management Systems, Inc. | Retention of Certain Business
Acquisition disclosures
Maximum potential contingent payments	$ 20,000