Stockholders' Equity - Additional Information (Detail)		3 Months Ended		5 Months Ended	9 Months Ended		12 Months Ended
	Jun. 30, 2016 Installment $ / shares shares	Sep. 30, 2016 USD ($) $ / shares shares	Sep. 30, 2015 USD ($) shares	Sep. 30, 2016 USD ($) $ / shares shares	Sep. 30, 2016 USD ($) $ / shares shares	Sep. 30, 2015 USD ($) shares	Dec. 31, 2015 $ / shares shares	Nov. 30, 2015 USD ($)
Class Of Stock [Line Items]
Capitalized stock-based compensation costs | $		$ 0	$ 0		$ 0	$ 0
Stock options granted		0	0		0	0
Share issued, exercise of options and release of stock awards					1,300,000		1,400,000
Shares settled for tax withholding					572,000	433,000
Stock repurchase program, authorized amount | $								$ 150,000,000
Common stock repurchased, shares		1,500,000			5,500,000
Common stock repurchased, amount | $		$ 19,000,000			$ 71,082,000	$ 0
Remaining value for purchase of common stock under the stock repurchase program | $		$ 79,000,000		$ 79,000,000	$ 79,000,000
Unregistered common stock, shares issued		267,868,000		267,868,000	267,868,000		266,545,000
Common stock, par value | $ / shares		$ 0.01		$ 0.01	$ 0.01		$ 0.01
Stock based compensation expense | $		$ 9,773,000	$ 9,192,000		$ 30,834,000	$ 28,728,000
Netsmart [Member]
Class Of Stock [Line Items]
Stock based compensation expense | $		1,724,000			3,150,000
Liability for outstanding awards | $		$ 3,200,000		$ 3,200,000	$ 3,200,000
Estimated weighted average fair value, Black-Scholes-Merton option pricing model | $ / shares		$ 0.45		$ 0.45	$ 0.45
Estimated share price | $ / shares		$ 1.00		$ 1.00	$ 1.00
Share based compensation expense remaining to be recognized | $		$ 25,400,000		$ 25,400,000	$ 25,400,000
Share based compensation expense remaining to be recognized, 2016 | $		1,800,000		1,800,000	1,800,000
Share based compensation expense remaining to be recognized, 2017 | $		7,100,000		7,100,000	7,100,000
Share based compensation expense remaining to be recognized, 2018 | $		7,100,000		7,100,000	7,100,000
Share based compensation expense remaining to be recognized, 2019 | $		7,100,000		7,100,000	7,100,000
Share based compensation expense remaining to be recognized, 2020 | $		2,300,000		$ 2,300,000	2,300,000
Netsmart [Member] | Class B Non Voting Common Units
Class Of Stock [Line Items]
Options issued during the period				89,889,000
Exercise price | $ / shares				$ 1.00
Intrinsic value related to outstanding Option Units | $		$ 0		$ 0	$ 0
Estimated weighted average fair value, Black-Scholes-Merton option pricing model | $ / shares		$ 0.45		$ 0.45	$ 0.45
Netsmart [Member] | Nathan Holding LLC 2016 Unit Option Plan [Member]
Class Of Stock [Line Items]
Stock options granted				89,889,000
Maximum issuance of options		116,491,000		116,491,000	116,491,000
Options available for further issuance		27,986,000		27,986,000	27,986,000
Exercise price | $ / shares				$ 1.00
Option Units, Forfeited during the period				1,384,000
Netsmart [Member] | Nathan Holding LLC 2016 Unit Option Plan [Member] | Time Based Option Units [Member]
Class Of Stock [Line Items]
Options issued during the period				64,198,000
Exercise price | $ / shares				$ 1.00
Option Units, Forfeited during the period				989,000
Options vesting period				4 years
Vesting description					The Option Units vest ratably over a period of four years, with the first twenty-five percent vesting at the first anniversary of the issuance and the remaining vesting in equal monthly increments over the following thirty-six months
Netsmart [Member] | Nathan Holding LLC 2016 Unit Option Plan [Member] | Performance Based Option Units [Member]
Class Of Stock [Line Items]
Options issued during the period				25,691,000
Exercise price | $ / shares				$ 1.00
Option Units, Forfeited during the period				395,000
Stock based compensation expense | $					$ 0
Netsmart [Member] | Nathan Holding LLC 2016 Unit Option Plan [Member] | Maximum [Member]
Class Of Stock [Line Items]
Option Units expiration period					10 years
Customary Anti-Dilution Adjustments [Member] | Warrant Issued to Commercial Partner [Member]
Class Of Stock [Line Items]
Number of installments | Installment	4
Number of warrants vesting annually	750,000
Warrant expiration period	2026-06
Case 1 [Member] | Customary Anti-Dilution Adjustments [Member] | Warrant Issued to Commercial Partner [Member]
Class Of Stock [Line Items]
Number of warrants issued	900,000
Common stock, par value | $ / shares	$ 0.01
Sale of common stock, price per share | $ / shares	$ 12.47
Case 2 [Member] | Customary Anti-Dilution Adjustments [Member] | Warrant Issued to Commercial Partner [Member]
Class Of Stock [Line Items]
Number of warrants issued	1,000,000
Sale of common stock, price per share | $ / shares	$ 14.34
Case 3 [Member] | Customary Anti-Dilution Adjustments [Member] | Warrant Issued to Commercial Partner [Member]
Class Of Stock [Line Items]
Number of warrants issued	1,100,000
Sale of common stock, price per share | $ / shares	$ 15.59