Debt - Additional Information (Detail)						1 Months Ended	12 Months Ended
	Feb. 15, 2018 USD ($)	Nov. 10, 2016 USD ($)	Oct. 27, 2016 USD ($)	Apr. 19, 2016 USD ($)	Jun. 18, 2013 USD ($) $ / shares	Jun. 30, 2013 USD ($)	Dec. 31, 2017 USD ($) $ / shares		Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2013 USD ($)	Mar. 31, 2019	Jul. 17, 2017 USD ($)	Sep. 30, 2015 USD ($)
Debt Instrument [Line Items]
Debt instrument capitalized amount										$ 3,300,000
Payments for 1.25% Call Option						$ 82,800,000
Proceeds from issuance of warrants, net of issuance costs						51,200,000
Net cash payment for 1.25% Notes call spread overlay						$ 31,600,000
Maximum percentage of foreign subsidiary capital stock guaranteeing credit facility							65.00%
Deferred debt issuance cost written off with existing Credit Facility							$ 0		$ 5,224,000	1,433,000
Debt instrument principal amount							$ 1,620,066,000		$ 1,386,813,000
HealthMEDX, LLC [Member]
Debt Instrument [Line Items]
Proceeds from debt			$ 36,195,000
Consideration paid for acquisitions			2,888,000
Letter of Credit [Member]
Debt Instrument [Line Items]
Portion of facility available for issuance of letters of credit														$ 50,000,000
Letter of Credit [Member] | Subsequent Event [Member]
Debt Instrument [Line Items]
Portion of facility available for issuance of letters of credit	$ 50,000,000
Line of Credit [Member]
Debt Instrument [Line Items]
Portion of facility available for issuance of swingline loans														10,000,000
Line of Credit [Member] | Subsequent Event [Member]
Debt Instrument [Line Items]
Portion of facility available for issuance of swingline loans	10,000,000
Netsmart Revolving Facility [Member]
Debt Instrument [Line Items]
Debt instrument, interest rate, effective percentage							6.44%
Netsmart Revolving Facility [Member] | LIBOR Rate [Member]
Debt Instrument [Line Items]
Senior secured credit facility interest rate spread							4.75%		4.75%
1.25% Cash Convertible Senior Notes [Member]
Debt Instrument [Line Items]
Debt instrument principal amount					$ 345,000,000
Proceeds from debt					$ 305,100,000
Interest payment, terms							Interest on the 1.25% Notes is payable semiannually in arrears on January 1 and July 1 of each year
Debt, Maturity date					Jul. 01, 2020		Jul. 01, 2020
Debt instrument convertible, principal amount					$ 1,000
Convertible number of equity instrument					58.1869
Conversion price per common stock | $ / shares					$ 17.19		$ 17.19
Repurchase percentage on principal					100.00%
Fair value liability of embedded cash conversion option					$ 82,800,000
Convertible debt instrument remaining discount amortization period							2 years 6 months
Debt instrument, interest rate, effective percentage					5.40%
Interest rate							1.25%
Debt Instrument, fees and aggregate cost					$ 8,400,000
Debt instrument capitalized amount					$ 8,300,000
Deferred charges capitalized amount outstanding							$ 2,900,000
Accrued and unpaid interest							2,200,000
Payments for 1.25% Call Option											$ 82,800,000
Debt instrument principal amount							$ 345,000,000	[1]	$ 345,000,000
1.25% Cash Convertible Senior Notes [Member] | Condition One [Member]
Debt Instrument [Line Items]
Threshold trading days							20 days
Threshold consecutive trading days							30 days
Debt instrument conversion price percentage							130.00%
1.25% Cash Convertible Senior Notes [Member] | Condition Two [Member]
Debt Instrument [Line Items]
Threshold trading days							5 days
Threshold consecutive trading days							5 days
Debt instrument conversion price percentage							98.00%
Debt instrument convertible, principal amount							$ 1,000
Senior Secured Term Loan [Member]
Debt Instrument [Line Items]
Credit facility, maximum borrowing capacity														250,000,000
Term Loan repayment, end date							Sep. 30, 2020
Credit facility, increase in total borrowing limits														25,000,000
Senior secured credit facilities term, years							5 years
Debt instrument principal amount							$ 218,750,000	[2]	218,800,000
Senior Secured Term Loan [Member] | Subsequent Event [Member]
Debt Instrument [Line Items]
Credit facility, maximum borrowing capacity	400,000,000
Credit facility, increase in total borrowing limits	$ 250,000,000
Senior secured credit facilities term, years	5 years
Senior Secured Revolving Facility [Member]
Debt Instrument [Line Items]
Credit facility, maximum borrowing capacity														550,000,000
Credit facility, increase in total borrowing limits														125,000,000
Credit facility, maximum borrowing capacity, foreign currencies														$ 100,000,000
Senior secured credit facilities term, years							5 years
Applicable margin for borrowings based on federal funds rate							0.50%
Initial margin for borrowings based on non-Eurocurrency rate							1.25%
Initial margin for borrowings based on Eurocurrency rate							2.25%
Basis point reduction in applicable interest rate margin ranges							0.50%
Debt instrument principal amount									410,000,000
Credit facility borrowing capacity, amount available							$ 139,200,000
Senior Secured Revolving Facility [Member] | Subsequent Event [Member]
Debt Instrument [Line Items]
Credit facility, maximum borrowing capacity	$ 900,000,000
Credit facility, increase in total borrowing limits	$ 550,000,000
Senior secured credit facilities term, years	5 years
Initial margin for borrowings based on non-Eurocurrency rate	1.00%
Initial margin for borrowings based on Eurocurrency rate	2.00%
Senior Secured Revolving Facility [Member] | Eurocurrency Rate for U.S. Dollars [Member]
Debt Instrument [Line Items]
Senior secured credit facility interest rate spread							1.00%
Senior Secured Revolving Facility [Member] | 2015 Credit Agreement [Member] | Base Rate [Member] | Minimum [Member]
Debt Instrument [Line Items]
Senior secured credit facility interest rate spread							0.00%
Senior Secured Revolving Facility [Member] | 2015 Credit Agreement [Member] | Base Rate [Member] | Maximum [Member]
Debt Instrument [Line Items]
Senior secured credit facility interest rate spread							1.25%
Senior Secured Revolving Facility [Member] | 2015 Credit Agreement [Member] | Eurocurrency Rate [Member] | Minimum [Member]
Debt Instrument [Line Items]
Senior secured credit facility interest rate spread							1.00%
Senior Secured Revolving Facility [Member] | 2015 Credit Agreement [Member] | Eurocurrency Rate [Member] | Maximum [Member]
Debt Instrument [Line Items]
Senior secured credit facility interest rate spread							2.25%
Senior Secured Credit Facility [Member]
Debt Instrument [Line Items]
Aggregate amount of additional credit facilities authorized							$ 300,000,000
Debt instrument principal amount							$ 628,750,000		441,875,000
Letters of credit outstanding									$ 800,000
Senior Secured Credit Facility [Member] | United States dollars [Member]
Debt Instrument [Line Items]
Debt instrument, interest rate, effective percentage									3.82%
Senior Secured Credit Facility [Member] | Minimum [Member]
Debt Instrument [Line Items]
Interest coverage ratio							400.00%
Senior Secured Credit Facility [Member] | Maximum [Member]
Debt Instrument [Line Items]
Leverage ratio							400.00%
Secured leverage ratio							300.00%
Senior Secured Credit Facility [Member] | LIBOR Rate [Member]
Debt Instrument [Line Items]
Senior secured credit facility interest rate spread									2.25%
Senior Secured Credit Facility [Member] | 2015 Credit Agreement [Member]
Debt Instrument [Line Items]
Debt Instrument, fees and aggregate cost										3,000,000
Debt issuance costs capitalized										2,700,000
Deferred debt issuance cost written off with existing Credit Facility										1,100,000
Debt Instrument fees and other costs expensed										$ 300,000
Senior Secured Credit Facility [Member] | 2015 Credit Agreement [Member] | Minimum [Member] | Covenant On Potential Acquisition [Member]
Debt Instrument [Line Items]
Consideration paid for acquisitions							$ 100,000,000
Senior Secured Credit Facility [Member] | 2015 Credit Agreement [Member] | Maximum [Member] | Covenant On Potential Acquisition [Member]
Debt Instrument [Line Items]
Leverage ratio							450.00%
Secured leverage ratio							325.00%
Netsmart First Lien Credit Agreement [Member]
Debt Instrument [Line Items]
Debt instrument, interest rate, effective percentage							6.19%		5.50%
Debt instrument capitalized amount		$ 0
Deferred debt issuance cost written off with existing Credit Facility		$ 5,200,000
Decrease in effective interest rate		(0.25%)
Netsmart First Lien Credit Agreement [Member] | Netsmart First Lien Term Loan [Member]
Debt Instrument [Line Items]
Credit facility, maximum borrowing capacity				$ 395,000,000
Senior secured credit facilities term, years				7 years
Debt instrument principal amount							$ 479,300,000
Credit facility termination date				Apr. 19, 2023
Netsmart First Lien Credit Agreement [Member] | DeVero, Inc. [Member]
Debt Instrument [Line Items]
Debt instrument capitalized amount							$ 1,300,000
Credit facility, maximum borrowing capacity													$ 51,000,000
Netsmart First Lien Credit Agreement [Member] | Minimum [Member] | Scenario Forecast [Member]
Debt Instrument [Line Items]
Leverage ratio												6.75%
Netsmart First Lien Credit Agreement [Member] | Maximum [Member]
Debt Instrument [Line Items]
Leverage ratio							7.50%
Netsmart First Lien Credit Agreement [Member] | LIBOR Rate [Member]
Debt Instrument [Line Items]
Senior secured credit facility interest rate spread				4.25%			4.50%		4.50%
Netsmart First Lien Credit Agreement [Member] | LIBOR Rate [Member] | Netsmart First Lien Term Loan [Member]
Debt Instrument [Line Items]
Senior secured credit facility interest rate spread				4.50%
Netsmart First Lien Credit Agreement [Member] | Alternate Base Rate Loans [Member]
Debt Instrument [Line Items]
Debt instrument, interest rate, effective percentage				3.25%
Netsmart First Lien Credit Agreement [Member] | Alternate Base Rate Loans [Member] | Netsmart First Lien Term Loan [Member]
Debt Instrument [Line Items]
Debt instrument, interest rate, effective percentage				3.50%
Netsmart First Lien Credit Agreement [Member] | Netsmart Revolving Facility [Member]
Debt Instrument [Line Items]
Credit facility, maximum borrowing capacity				$ 50,000,000
Senior secured credit facilities term, years				5 years
Credit facility borrowing capacity, amount available							$ 50,000,000
Credit facility termination date				Apr. 19, 2021
Credit facility borrowing capacity, additional amount available							$ 200,200,000
Netsmart First Lien Credit Agreement [Member] | Netsmart Revolving Facility [Member] | LIBOR Rate [Member]
Debt Instrument [Line Items]
Senior secured credit facility interest rate spread				4.75%
Netsmart First Lien Credit Agreement [Member] | Netsmart Revolving Facility [Member] | Alternate Base Rate Loans [Member]
Debt Instrument [Line Items]
Debt instrument, interest rate, effective percentage				3.75%
Netsmart Second Lien Credit Agreement [Member]
Debt Instrument [Line Items]
Debt instrument, interest rate, effective percentage							10.98%		10.50%
Netsmart Second Lien Credit Agreement [Member] | Netsmart Second Lien Term Loan [Member]
Debt Instrument [Line Items]
Credit facility, maximum borrowing capacity				$ 167,000,000
Senior secured credit facilities term, years				7 years 6 months
Debt instrument principal amount							$ 167,000,000
Credit facility termination date				Oct. 19, 2023
Netsmart Second Lien Credit Agreement [Member] | Minimum [Member] | Scenario Forecast [Member]
Debt Instrument [Line Items]
Leverage ratio												7.75%
Netsmart Second Lien Credit Agreement [Member] | Maximum [Member]
Debt Instrument [Line Items]
Leverage ratio							8.50%
Netsmart Second Lien Credit Agreement [Member] | LIBOR Rate [Member]
Debt Instrument [Line Items]
Senior secured credit facility interest rate spread							9.50%		9.50%
Netsmart Second Lien Credit Agreement [Member] | LIBOR Rate [Member] | Netsmart Second Lien Term Loan [Member]
Debt Instrument [Line Items]
Senior secured credit facility interest rate spread				9.50%
Netsmart Second Lien Credit Agreement [Member] | Alternate Base Rate Loans [Member] | Netsmart Second Lien Term Loan [Member]
Debt Instrument [Line Items]
Debt instrument, interest rate, effective percentage				8.50%
Netsmart Credit Agreements [Member]
Debt Instrument [Line Items]
Debt issuance costs capitalized									$ 27,900,000
Netsmart First Lien Term Loan [Member]
Debt Instrument [Line Items]
Debt instrument principal amount							$ 479,316,000
Netsmart First Lien Term Loan [Member] | HealthMEDX, LLC [Member]
Debt Instrument [Line Items]
Debt instrument capitalized amount			600,000
Credit facility, maximum borrowing capacity			$ 40,000,000

[1] Assumes no cash conversions of the 1.25% Notes prior to their maturity on July 1, 2020.

[2] Assumes no additional borrowings after December 31, 2017 and that all drawn amounts are repaid upon maturity.