Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Revenues:
Professional employer service fees	$ 673,924	$ 572,286	$ 470,522
Staffing services	166,662	168,555	165,833
Total revenues	840,586	740,841	636,355
Cost of revenues:
Direct payroll costs	126,753	127,964	126,399
Payroll taxes and benefits	357,867	312,284	263,100
Workers' compensation	210,430	171,137	213,451
Total cost of revenues	695,050	611,385	602,950
Gross margin	145,536	129,456	33,405
Selling, general and administrative expenses	113,342	90,177	74,065
Depreciation and amortization	3,253	2,851	2,506
Income (loss) from operations	28,941	36,428	(43,166)
Other (expense) income:
Investment income, net	956	771	543
Interest expense	(807)	(1,965)	(173)
Loss on litigation	(3,544)	0	0
Other, net	40	(88)	152
Other (expense) income, net	(3,355)	(1,282)	522
Income (loss) before income taxes	25,586	35,146	(42,644)
Provision for (benefit from) income taxes	6,787	9,652	(17,098)
Net income (loss)	$ 18,799	$ 25,494	$ (25,546)
Basic earnings (loss) per common share	$ 2.60	$ 3.55	$ (3.57)
Weighted average number of basic common shares outstanding	7,226	7,173	7,160
Diluted earnings (loss) per common share	$ 2.55	$ 3.47	$ (3.57)
Weighted average number of diluted common shares outstanding	7,378	7,353	7,160