Condensed consolidated statements of changes in members' deficit/shareholders' equity - USD ($) $ in Thousands	Total Members' Deficit/ Shareholders' Equity	Common Stock Class A common stock	Common Stock Class B common stock	Additional Paid-In Capital	Accumulated Deficit	Accumulated Other Comprehensive Loss	Common Units	Non-controlling Interest	Total
Beginning balance at Dec. 31, 2017	$ (778,661)			$ 30,731	$ (805,470)	$ (8,269)	$ 4,347		$ (778,661)
Increase (Decrease) in MEMBERS' DEFICIT
Net income (loss)	(19,710)				(19,710)				(19,710)
Issuance of restricted common units in connection with acquisitions and contingent consideration	32,829						32,829		32,829
Non-cash equity compensation expense	7,555			7,555					7,555
Currency translation adjustment - net of tax	(1,506)					(1,506)			(1,506)
Distributions for unitholders	(50)				(50)				(50)
Ending balance at Jun. 30, 2018	(759,543)			38,286	(825,230)	(9,775)	37,176		(759,543)
Beginning balance at Mar. 31, 2018	(780,629)			34,585	(817,492)	(8,653)	10,931		(780,629)
Increase (Decrease) in MEMBERS' DEFICIT
Net income (loss)	(7,656)				(7,656)				(7,656)
Issuance of restricted common units in connection with acquisitions and contingent consideration	26,245						26,245		26,245
Non-cash equity compensation expense	3,701			3,701					3,701
Currency translation adjustment - net of tax	(1,122)					(1,122)			(1,122)
Distributions for unitholders	(82)				(82)				(82)
Ending balance at Jun. 30, 2018	(759,543)			38,286	(825,230)	(9,775)	$ 37,176		(759,543)
Beginning balance at Dec. 31, 2018	469,662	$ 462	$ 228	471,386	(590)	(1,824)		$ 342,858	812,520
Beginning balance (in shares) at Dec. 31, 2018		46,265,903	22,823,272
Increase (Decrease) in MEMBERS' DEFICIT
Net income (loss)	(2,146)				(2,146)			2,420	274
Issuance (cancellation) of common stock in connection with exercise of Focus LLC common unit exchange rights	16,572	$ 6	$ (5)	16,571					16,572
Issuance (cancellation) of common stock in connection with exercise of Focus LLC common unit exchange rights (in shares)		514,826	(514,826)
Issuance of common stock in connection with exercise of Focus LLC incentive unit exchange rights	9,975	$ 3		9,972					9,975
Issuance of common stock in connection with exercise of Focus LLC incentive unit exchange rights (in shares)		312,871
Forfeiture of unvested Class A common stock	(30)			(30)					(30)
Forfeiture of unvested common stock		(909)
Exercise of stock options	796			796					796
Exercise of stock options (in shares)		24,126
Change in non-controlling interest allocation	(11,032)			(11,032)				(14,790)	(25,822)
Non-cash equity compensation expense	1,653			1,653					1,653
Currency translation adjustment - net of tax	(176)					(176)		(157)	(333)
Adjustment of deferred tax assets, net of amounts payable under tax receivable agreements and changes from Focus LLC interest transactions	250			250					250
Ending balance at Jun. 30, 2019	485,524	$ 471	$ 223	489,566	(2,736)	(2,000)		330,331	815,855
Ending Balance (in shares) at Jun. 30, 2019		47,116,817	22,308,446
Beginning balance at Mar. 31, 2019	455,054	$ 467	$ 225	459,488	(3,532)	(1,594)		357,222	812,276
Beginning balance (in shares) at Mar. 31, 2019		46,675,183	22,568,831
Increase (Decrease) in MEMBERS' DEFICIT
Net income (loss)	796				796			2,306	3,102
Issuance (cancellation) of common stock in connection with exercise of Focus LLC common unit exchange rights	7,305	$ 3	$ (2)	7,304					7,305
Issuance (cancellation) of common stock in connection with exercise of Focus LLC common unit exchange rights (in shares)		260,385	(260,385)
Issuance of common stock in connection with exercise of Focus LLC incentive unit exchange rights	4,538	$ 1		4,537					4,538
Issuance of common stock in connection with exercise of Focus LLC incentive unit exchange rights (in shares)		163,600
Exercise of stock options	582			582					582
Exercise of stock options (in shares)		17,649
Change in non-controlling interest allocation	17,315			17,315				(28,916)	(11,601)
Non-cash equity compensation expense	948			948					948
Currency translation adjustment - net of tax	(406)					(406)		(281)	(687)
Adjustment of deferred tax assets, net of amounts payable under tax receivable agreements and changes from Focus LLC interest transactions	(608)			(608)					(608)
Ending balance at Jun. 30, 2019	$ 485,524	$ 471	$ 223	$ 489,566	$ (2,736)	$ (2,000)		$ 330,331	$ 815,855
Ending Balance (in shares) at Jun. 30, 2019		47,116,817	22,308,446