CONSOLIDATED BALANCE SHEETS (Unaudited) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Current assets:
Cash and cash equivalents	$ 227,432	$ 264,544
Restricted cash	47,374	47,149
Marketable securities	51,397	16,904
Accounts receivable, net:
Trade	2,465	6,931
Unbilled	196,141	181,040
Other	2,594	2,415
Prepaid insurance	16,887	15,620
Other current assets	13,759	9,651
Deferred income taxes	3,110	7,211
Total current assets	561,159	551,465
Property and equipment:
Land	4,115	4,115
Buildings and improvements	69,012	68,583
Computer hardware and software	82,801	81,140
Software development costs	36,284	35,866
Furniture and fixtures	36,712	36,717
Aircraft	35,879	35,879
Total property and equipment, gross	264,803	262,300
Accumulated depreciation and amortization	(172,653)	(168,358)
Total property and equipment, net	92,150	93,942
Other assets:
Prepaid health insurance	9,000	9,000
Deposits - health insurance	3,000	3,000
Deposits - workers' compensation	67,528	64,201
Goodwill and other intangible assets, net	23,274	23,775
Other assets	4,600	4,817
Total other assets	107,402	104,793
Total assets	760,711	750,200
Current liabilities:
Accounts payable	2,202	3,660
Payroll taxes and other payroll deductions payable	183,511	178,534
Accrued worksite employee payroll cost	168,715	150,070
Accrued health insurance costs	7,484	13,942
Accrued workers' compensation costs	49,902	49,484
Accrued corporate payroll and commissions	15,523	23,537
Other accrued liabilities	15,348	12,478
Income tax payable	4,774	4,054
Total current liabilities	447,459	435,759
Noncurrent liabilities:
Accrued workers' compensation costs	65,702	64,536
Deferred income taxes	8,162	9,000
Total noncurrent liabilities	73,864	73,536
Commitments and contingencies
Stockholders' equity:
Common stock	308	308
Additional paid-in capital	133,898	133,207
Treasury stock, at cost	(144,998)	(133,950)
Accumulated other comprehensive income, net of tax	32	16
Retained earnings	250,148	241,324
Total stockholders' equity	239,388	240,905
Total liabilities and stockholders' equity	$ 760,711	$ 750,200