CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) (USD $)	9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010
Cash flows from operating activities:
Net income	$ 19,626,000	$ 14,651,000
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	11,335,000	11,266,000
Loss on exchange of assets	4,396,000	0
Amortization of marketable securities	1,535,000	1,148,000
Stock-based compensation	6,455,000	6,148,000
Deferred income taxes	(96,000)	1,692,000
Changes in operating assets and liabilities, net of effects from acquisitions:
Restricted cash	(1,608,000)	(3,225,000)
Accounts receivable	(20,231,000)	(28,665,000)
Prepaid insurance	9,796,000	(1,285,000)
Other current assets	(2,339,000)	(2,227,000)
Other assets	4,876,000	8,350,000
Accounts payable	(650,000)	21,000
Payroll taxes and other payroll deductions payable	(40,892,000)	(48,195,000)
Accrued worksite employee payroll expense	21,091,000	70,315,000
Accrued health insurance costs	(10,210,000)	4,041,000
Accrued workers' compensation costs	6,013,000	6,199,000
Accrued corporate payroll, commissions and other accrued liabilities	3,656,000	4,851,000
Income taxes payable/receivable	479,000	2,566,000
Total adjustments	(6,394,000)	33,000,000
Net cash provided by operating activities	13,232,000	47,651,000
Cash flows from investing activities:
Marketable securities purchases	(43,607,000)	(56,775,000)
Marketable securities proceeds from dispositions	3,907,000	2,748,000
Marketable securities proceeds from maturities	26,194,000	15,890,000
Cash exchanged for acquisitions	(13,125,000)	(12,886,000)
Property and equipment	(23,404,000)	(4,349,000)
Net cash used in investing activities	(50,035,000)	(55,372,000)
Cash flows from financing activities:
Purchase of treasury stock	(22,459,000)	(7,852,000)
Dividends paid	(11,871,000)	(10,148,000)
Proceeds from the exercise of stock options	3,881,000	5,505,000
Income tax benefit from stock-based compensation	2,049,000	432,000
Other	284,000	629,000
Net cash used in financing activities	(28,116,000)	(11,434,000)
Net decrease in cash and cash equivalents	(64,919,000)	(19,155,000)
Cash and cash equivalents at beginning of period	234,829,000	227,085,000
Cash and cash equivalents at end of period	169,910,000	207,930,000
Supplemental Cash Flow Information:
Fair value of traded-in aircraft	4,000,000
Additional cash paid to acquire replacement aircraft	10,000,000
Non-cash loss included in other income (expense)	$ (4,400,000)