Income Taxes (Details) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Deferred tax liabilities:
Prepaid assets	$ (9,268,000)	$ (10,051,000)
Depreciation	(8,616,000)	(8,390,000)
Software development costs	(2,858,000)	(1,198,000)
Other	(1,137,000)	(751,000)
Total deferred tax liabilities	(21,879,000)	(20,390,000)
Deferred tax assets:
Accrued incentive compensation	3,877,000	3,100,000
Net operating loss carryforward	2,290,000	2,360,000
Workers' compensation accruals	3,744,000	3,055,000
Long-term capital loss carry-forward	148,000	188,000
Accrued rent	1,132,000	1,260,000
Stock-based compensation	2,908,000	2,657,000
Uncollectible accounts receivable	389,000	375,000
Total deferred tax assets	14,488,000	12,995,000
Valuation allowance	(148,000)	(188,000)
Total net deferred tax assets	14,340,000	12,807,000
Net deferred tax liabilities	(7,539,000)	(7,583,000)
Net current deferred tax assets (liabilities)	3,233,000	1,267,000
Net noncurrent deferred tax liabilities	(10,772,000)	(8,850,000)
Current income tax expense:
Federal	16,816,000	12,668,000	14,478,000
State	3,535,000	1,734,000	1,994,000
Total current income tax expense	20,351,000	14,402,000	16,472,000
Deferred income tax (benefit) expense:
Federal	47,000	1,033,000	(4,162,000)
State	(93,000)	146,000	(235,000)
Total deferred income tax (benefit) expense	(46,000)	1,179,000	(4,397,000)
Total income tax expense	20,305,000	15,581,000	12,075,000
Net income tax expense (benefit) on nonqualified stock option exercises	1,663,000	25,000	(372,000)
Income Tax Reconciliation [Abstract]
Assumed income tax rate	35.00%	35.00%	35.00%
Expected income tax expense at 35%	17,770,000	13,307,000	10,027,000
State income taxes, net of federal benefit	2,249,000	1,273,000	1,053,000
Nondeductible expenses	904,000	1,092,000	1,093,000
Tax-exempt interest income	(558,000)	0	0
Other, net	(60,000)	(91,000)	(98,000)
Reported total income tax expense	20,305,000	15,581,000	12,075,000
Capital loss carryforwards	400,000
Capital loss carryforwards, expiration date	2012
Valuation allowance for capital loss carryforward	400,000
Business Acquisition [Line Items]
Net operating loss carryforwards	2,290,000	2,360,000
ExpensAble [Member]
Deferred tax assets:
Net operating loss carryforward	6,100,000
Business Acquisition [Line Items]
Net operating loss carryforwards	$ 6,100,000
Net operating loss carryforwards, expiration date	2021 to 2030