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Maximum amount the employee may contribute to a defined contribution plan.

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Percentage of domestic federal statutory tax rate applicable to pretax income (loss).

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Amount of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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Fair value of share-based awards for which the grantee gained the right by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash.

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Net number of non-option equity instruments granted to participants.

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Period from grant date that an equity-based award expires, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Note 14 - Employee Benefits (Details Textual) - USD ($)	1 Months Ended											12 Months Ended			37 Months Ended
Note 14 - Employee Benefits (Details Textual) - USD ($)	Dec. 31, 2018	Aug. 31, 2018	May 31, 2018	Aug. 31, 2017	May 31, 2017	Aug. 31, 2016	May 31, 2016	May 31, 2015	May 31, 2014	May 31, 2013	May 31, 2012	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	May 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Granted												998,022
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized	1,333,333											1,333,333
Share Based Compensation Arrangement By Share Based Payment Award Fair Value Assumptions Expected Forfeiture Rate Of Unvested Outstanding Awards												1.25%
Allocated Share-based Compensation Expense, Total												$ 3,323,000	$ 1,250,000	$ 883,000
Allocated Share-based Compensation Expense, Net of Tax												$ 2,600,000	$ 738,000	$ 547,000
Allocated Share Based Compensation Expense Net Of Tax Amount Per Basic And Diluted Share												$ 0.05	$ 0.01	$ 0.01
Income Tax Expense (Benefit), Total												$ 16,002,000	$ (33,811,000)	$ 23,602,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number, Ending Balance	939,193											939,193	918,583
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term												3 years 292 days
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Intrinsic Value	$ 3,000,000											$ 3,000,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Number	545,713											545,713
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Remaining Contractual Term												2 years 255 days
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Intrinsic Value	$ 2,600,000											$ 2,600,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Intrinsic Value												1,500,000	$ 830,000	1,900,000
Proceeds from Stock Options Exercised												938,000	1,100,000	4,400,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested in Period, Fair Value												$ 547,000	515,000	$ 534,000
Income Tax Expense (Benefit), Continuing Operations, Adjustment of Deferred Tax (Asset) Liability													$ (56,500,000)
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent												21.00%	35.00%	35.00%
Defined Contribution Plan, Employer Matching Contribution, Percent of Match												35.00%
Defined Contribution Plan, Employer Matching Contribution, Percent of Employees' Gross Pay												6.00%
Defined Contribution Plan, Employers Matching Contribution, Annual Vesting Percentage												20.00%
Defined Contribution Plan, Employer Discretionary Contribution Amount												$ 0	$ 0	$ 0
Defined Contribution Plan, Cost												2,300,000	2,100,000	2,100,000
Retirement Savings Plan, Participants Less Than 50 Years Old [Member]
Defined Contribution Plan, Maximum Annual Contributions Per Employee, Amount												18,500
Retirement Savings Plan, Participants Over50 Years Old [Member]
Defined Contribution Plan, Maximum Annual Contributions Per Employee, Amount												24,500
Accounting Standards Update 2016-09 [Member]
Income Tax Expense (Benefit), Total												$ 319,000	176,000
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period												5 years			5 years
Share-based Compensation Arrangement By Share-based Payment Awards, Annual Service Vesting Percentage															5.00%
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Fair Value												$ 2,700,000
Performance Shares [Member] \| One Half of Awards Paid Immediately Upon Vesting and One Half Credited to Employees' Accounts [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Granted			45,700		109,169		57,669	58,335	60,668	104,250	98,750
Share-based Compensation Arrangement By Share-based Payment Awards, Annual Service Vesting Percentage					10.00%
Performance Shares [Member] \| Awards Paid to Employees Upon Vesting [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Granted	2,000	2,000	28,000	2,000	43,342	1,667	21,671	32,500	18,337
Unvested Service Based Option Awards [Member]
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Total	$ 1,600,000											$ 1,600,000
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition												3 years 73 days
Unvested Performance Unit Awards [Member]
Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Total	$ 2,400,000											$ 2,400,000
Service Based Options [Member]
Stock Granted, Value, Share-based Compensation, Gross												$ 957,000	$ 592,000	$ 227,000
Two Thousand and Fifteen Plan [Member] \| Employee Stock Option [Member]
Share Based Compensation Arrangement By Share Based Payment Award Annual Percentage Of Award Which Vests												20.00%
Share Based Compensation Arrangement By Share Based Payment Award Number Of Shares Reserved For Issuance Under Awards Outstanding	568,873											568,873
Two Thousand and Fifteen Plan [Member] \| Performance Shares [Member]
Share Based Compensation Arrangement By Share Based Payment Award Number Of Shares Reserved For Issuance Under Awards Outstanding	349,814											349,814
Two Thousand And Five Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant	0											0
Two Thousand And Five Plan [Member] \| Employee Stock Option [Member]
Share Based Compensation Arrangement By Share Based Payment Award Number Of Shares Reserved For Issuance Under Awards Outstanding	370,320											370,320
Two Thousand And Five Plan [Member] \| Performance Shares [Member]
Share Based Compensation Arrangement By Share Based Payment Award Number Of Shares Reserved For Issuance Under Awards Outstanding	0											0
Minimum [Member] \| Two Thousand and Fifteen Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period												7 years
Maximum [Member] \| Two Thousand and Fifteen Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period												10 years