Income Taxes (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Deferred tax liabilities:
Prepaid assets	$ (3,957,000)	$ (7,133,000)
Depreciation	(2,021,000)	(936,000)
Software development costs	(3,732,000)	(3,960,000)
Total deferred tax liabilities	(9,710,000)	(12,029,000)
Deferred tax assets:
Accrued incentive compensation	3,510,000	8,590,000
Net operating loss carryforward	774,000	1,300,000
Workers’ compensation accruals	4,586,000	7,891,000
Accrued rent	676,000	1,092,000
Stock-based compensation	4,233,000	6,217,000
Intangibles	4,000	618,000
Minority investment impairment	667,000	1,021,000
Other	212,000	349,000
Total deferred tax assets	14,662,000	27,078,000
Valuation allowance	(669,000)	(1,024,000)
Total net deferred tax assets	13,993,000	26,054,000
Net deferred tax assets	4,283,000	14,025,000
Current income tax expense:
Federal	30,009,000	31,045,000	$ 35,221,000
State	5,988,000	5,190,000	5,741,000
Total current income tax expense	35,997,000	36,235,000	40,962,000
Deferred income tax (benefit) expense:
Federal	9,549,000	2,641,000	(13,632,000)
State	193,000	310,000	(1,101,000)
Total deferred income tax (benefit) expense	9,742,000	2,951,000	(14,733,000)
Total income tax expense	45,739,000	39,186,000	26,229,000
Income tax benefit recognized related to Equity Compensation after adoption of ASU 2016-09, Quantification	$ 6,800,000	$ 1,500,000
Income tax benefit recognized related to Equity Compensation after adoption of ASU 2016-09, per share	$ 0.16	$ 0.04
Net income tax expense (benefit) on nonqualified stock option exercises			2,216,000
Reconciliation of income tax expense [Abstract]
Assumed income tax rate (in hundredths)	35.00%
Expected income tax expense at 35%	$ 45,549,000	$ 36,812,000	22,967,000
State income taxes, net of federal benefit	4,085,000	3,684,000	2,696,000
Nondeductible expenses	2,649,000	1,669,000	1,669,000
Section 199 benefits	(875,000)	(686,000)	(627,000)
Equity compensation	(6,218,000)	(1,338,000)	0
Research and development credit	(634,000)	(751,000)	(530,000)
Effective Income Tax Rate Reconciliation, Tax Credit, Other, Amount	(669,000)	0	0
Effective Income Tax Rate Reconciliation, Change in Enacted Tax Rate, Amount	2,559,000	0	0
Other, net	(707,000)	(204,000)	54,000
Total income tax expense	45,739,000	39,186,000	26,229,000
Business Acquisition [Line Items]
Liability for Uncertain Tax Positions, Current	0	$ 0	$ 0
Enactment of US Tax Reform	2,500,000
ExpensAble [Member]
Business Acquisition [Line Items]
Operating Loss Carryforwards	$ 3,100,000
Minimum [Member] | ExpensAble [Member]
Business Acquisition [Line Items]
Net operating loss carryforwards, expiration date	Jan. 01, 2023
Maximum [Member] | ExpensAble [Member]
Business Acquisition [Line Items]
Net operating loss carryforwards, expiration date	Jan. 01, 2030