Unaudited Summarized Quarterly Financial Information (Schecule of Effects of Corrections of Errors on Unaudited Quarterly Results of Operations) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Quarterly Financial Information Disclosure [Line Items]
Net service revenues	$ 139,669	$ 137,716	$ 131,258	$ 109,476	$ 112,028	$ 108,662	$ 103,629	$ 101,675	$ 518,119	$ 425,994	$ 400,929
Gross profit	37,810	36,790	35,743	27,933	30,785	29,123	28,581	27,386	138,276	115,875	106,336
Operating income from continuing operations	6,809	5,988	6,913	4,589	7,470	5,877	5,991	7,030	24,299	26,368	15,476
Net income from continuing operations	4,542	3,631	4,318	4,886	3,000	3,464	2,756	4,314	17,377	13,534	12,063
Net income	$ 4,668	$ 3,631	$ 4,318	$ 4,886	$ 3,147	$ 3,464	$ 2,756	$ 4,314	$ 17,503	$ 13,681	$ 12,160
Basic	$ 0.36	$ 0.29	$ 0.37	$ 0.42	$ 0.27	$ 0.30	$ 0.24	$ 0.38	$ 1.45	$ 1.19	$ 1.07
Diluted	$ 0.35	$ 0.28	$ 0.36	$ 0.42	$ 0.27	$ 0.29	$ 0.24	$ 0.37	$ 1.41	$ 1.17	$ 1.07
As Previously Reported [Member]
Quarterly Financial Information Disclosure [Line Items]
Net service revenues		$ 137,631	$ 131,237	$ 109,448	$ 111,958	$ 108,592	$ 103,559	$ 101,606		$ 425,715	$ 400,688
Gross profit		36,705	35,722	27,905	30,715	29,053	28,511	27,317		115,596	106,095
Operating income from continuing operations		5,903	6,892	4,561	7,550	5,807	5,921	6,961		26,239	15,235
Net income from continuing operations		3,546	4,297	4,858	3,094	3,408	2,700	4,259		13,461	11,927
Net income		$ 3,546	$ 4,297	$ 4,858	$ 3,241	$ 3,408	$ 2,700	$ 4,259		13,608	12,024
Basic		$ 0.29	$ 0.37	$ 0.42	$ 0.28	$ 0.30	$ 0.24	$ 0.37
Diluted		$ 0.28	$ 0.36	$ 0.42	$ 0.28	$ 0.29	$ 0.23	$ 0.37
Corrections [Member]
Quarterly Financial Information Disclosure [Line Items]
Net service revenues		$ 85	$ 21	$ 28	$ 70	$ 70	$ 70	$ 69		279	241
Gross profit		85	21	28	70	70	70	69		279	241
Operating income from continuing operations		85	21	28	(80)	70	70	69		129	241
Net income from continuing operations		85	21	28	(94)	56	56	55		73	136
Net income		$ 85	$ 21	$ 28	$ (94)	$ 56	$ 56	$ 55		$ 73	$ 136
Basic					$ (0.01)			$ 0.01
Diluted					$ (0.01)		$ 0.01