Condensed Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Revenues:
Professional employer service fees	$ 187,718	$ 165,776	$ 359,927	$ 320,452
Staffing services	37,856	37,641	75,644	73,932
Total revenues	225,574	203,417	435,571	394,384
Cost of revenues:
Direct payroll costs	28,486	28,223	57,196	55,649
Payroll taxes and benefits	93,946	82,885	209,346	186,645
Workers' compensation	58,928	50,056	114,365	99,450
Total cost of revenues	181,360	161,164	380,907	341,744
Gross margin	44,214	42,253	54,664	52,640
Selling, general and administrative expenses	28,060	28,490	54,670	50,394
Depreciation and amortization	985	769	1,927	1,518
Income (loss) from operations	15,169	12,994	(1,933)	728
Other income (expense):
Investment income	1,392	259	1,550	507
Interest expense	(62)	(248)	(145)	(508)
Other, net	(4)	(5)	(4)	(1)
Other income (expense), net	1,326	6	1,401	(2)
Income (loss) before income taxes	16,495	13,000	(532)	726
Provision for (benefit from) income taxes	5,369	4,478	(431)	207
Net income (loss)	$ 11,126	$ 8,522	$ (101)	$ 519
Basic income (loss) per common share	$ 1.53	$ 1.18	$ (0.01)	$ 0.07
Weighted average number of basic common shares outstanding	7,254	7,210	7,252	7,209
Diluted income (loss) per common share	$ 1.47	$ 1.16	$ (0.01)	$ 0.07
Weighted average number of diluted common shares outstanding	7,550	7,328	7,252	7,323
Cash dividends per common share	$ 0.25	$ 0.22	$ 0.50	$ 0.44