Organization and Summary of Significant Accounting Policies - Narrative (Details)		12 Months Ended
	Jan. 01, 2019 segment	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($) segment	Dec. 31, 2017 USD ($)
Accounting Policies [Line Items]
Revenues		$ 897,027,000	$ 787,309,000	$ 712,714,000
Net income		61,338,000	37,729,000	30,518,000
Selling, general, and administrative expense		(289,916,000)	$ (263,095,000)	(241,470,000)
Number of operating segments | segment	1		2
Number of reporting segments | segment	1		2
Deferred revenues, net of cost of goods sold		97,977,000	$ 92,417,000
Deferred revenues, net of cost of goods sold, expected to be completed within one year		$ 90,894,000	81,835,000
Recognition period		five years
Fees to GPOs		$ 11,100,000	8,700,000	7,400,000
Amortization period for capitalized contract costs		10 years
Initial term and renewal service periods		10 years
Contract cost expense		$ 24,400,000	21,100,000	17,900,000
Impairment loss related to capitalized prepaid commissions		0
Non-recourse accounts receivable transferred		48,300,000	46,600,000	40,000,000.0
Accounts receivable due from third-party leasing companies for transferred non-recourse accounts receivable		4,600,000	10,600,000
Minimum required purchase obligation		65,900,000
Cost of revenues		460,115,000	414,979,000	394,077,000
Amortization of capitalized software development costs		17,500,000	12,500,000	9,700,000
Accumulated impairment loss on goodwill		$ 0
Minimum
Accounting Policies [Line Items]
Original terms of contracts		1 year
Estimated useful life of software-related products		3 years
Estimated useful lives of intangible assets		1 year
Maximum
Accounting Policies [Line Items]
Original terms of contracts		5 years
Estimated useful life of software-related products		5 years
Estimated useful lives of intangible assets		30 years
Internal Use Software and Software Development Costs
Accounting Policies [Line Items]
Useful life of property and equipment		5 years
Property and Equipment | Internal Use Software and Software Development Costs
Accounting Policies [Line Items]
Software development costs capitalized		$ 300,000	1,100,000
Other Assets
Accounting Policies [Line Items]
Software development costs capitalized		45,800,000	30,700,000
Primary Supplier
Accounting Policies [Line Items]
Minimum required purchase obligation		$ 0
Period for notice of termination		6 months
Purchases from suppliers		$ 75,100,000	54,800,000	64,500,000
Revolving Credit Facility
Accounting Policies [Line Items]
Term of debt instrument		5 years
Customer Concentration Risk | Revenues | Ten Largest GPOs
Accounting Policies [Line Items]
Concentration risk percentage		64.00%
Customer Concentration Risk | Lease Receivable | U.S. Government Hospitals
Accounting Policies [Line Items]
Concentration risk percentage		53.00%
Shipping Costs | Selling, General and Administrative Expense
Accounting Policies [Line Items]
Cost of revenues		$ 15,900,000	$ 14,100,000	$ 13,600,000