Stockholders' Equity - Additional Information (Detail) - USD ($)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017	Aug. 02, 2018	Dec. 31, 2016	Nov. 17, 2016
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			1,500,000		1,300,000
Shares settled for tax withholding			629,000	569,000
Common stock repurchased, amount			$ 101,905,000	$ 12,077,000
Netsmart [Member]
Class Of Stock [Line Items]
Stock options granted	1,400,000		1,400,000
Stock based compensation expense (benefit)	$ 1,100,000	$ 2,400,000	$ 3,500,000	$ (600,000)
Liability for outstanding awards	$ 11,600,000		$ 11,600,000
Estimated weighted average fair value, Black-Scholes-Merton option pricing model	$ 0.30		$ 0.30				$ 0.54
November 2016 Stock Repurchase Program [Member]
Class Of Stock [Line Items]
Stock repurchase program, authorized amount								$ 200,000,000
Common stock repurchased, shares	0	0	7,700,000	1,000,000
Common stock repurchased, amount			$ 101,900,000	$ 12,100,000
August 2018 Stock Repurchase Program [Member]
Class Of Stock [Line Items]
Stock repurchase program, authorized amount						$ 250,000,000
Common stock repurchased, shares			0