DEBT (Details - Revolving Credit Facility) - USD ($)		3 Months Ended
	Nov. 21, 2017	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018	Oct. 26, 2018
Line of Credit Facility [Line Items]
Long-term Debt, Current Maturities		$ 185,000,000		$ 125,000,000
Long-term Debt, Weighted Average Interest Rate, at Point in Time		3.99%		4.02%
Ratio of Debt to EBITDA Step-Down	4.0
Ratio of Debt to EBITDA Increase	0.5
Interest Expense, Debt		$ 3,800,000	$ 3,600,000
Debt Instrument, Unused Borrowing Capacity, Fee		100,000	200,000
Amortization of debt issuance costs		483,000	434,000
Revolving Credit Facility
Line of Credit Facility [Line Items]
Current borrowing capacity	$ 250,000,000.0				$ 350,000,000
Revolving Credit Facility, term	5 years
Revolving Credit Facility, conditional increase to borrowing capacity	$ 100,000,000.0
Increase in borrowing capacity					$ 100,000,000.0
Revolving Credit Facility, collateral, percent of assets	100.00%
Revolving Credit Facility, collateral, percent of equity	100.00%
Revolving Credit Facility, letter of credit fronting fee percentage	0.125%
Fees and expense paid to lenders at closing	$ 500,000
Line of Credit Facility, Collateral, Percent of Domestic Subsidiaries Equity	100.00%
Line of Credit Facility, Collateral, Percent of Voting Equity	66.00%
Line of Credit Facility, Collateral, Percent of Non-Voting Equity	100.00%
Swingline Facility [Member]
Line of Credit Facility [Line Items]
Current borrowing capacity	$ 10,000,000.0
Letters of Credit [Member]
Line of Credit Facility [Line Items]
Current borrowing capacity	$ 10,000,000.0
Federal Funds Effective Swap Rate [Member] | Revolving Credit Facility
Line of Credit Facility [Line Items]
Revolving Credit Facility, basis spread on variable rate	0.50%
London Interbank Offered Rate (LIBOR) [Member] | Revolving Credit Facility
Line of Credit Facility [Line Items]
Revolving Credit Facility, basis spread on variable rate	1.00%
Minimum | Revolving Credit Facility
Line of Credit Facility [Line Items]
Revolving Credit Facility, unused capacity, commitment fee percentage	0.25%
Revolving Credit Facility, letter of credit participation fee percentage	1.25%
Minimum | London Interbank Offered Rate (LIBOR) [Member] | Revolving Credit Facility
Line of Credit Facility [Line Items]
Revolving Credit Facility, basis spread on variable rate	1.25%
Minimum | Base Rate [Member] | Revolving Credit Facility
Line of Credit Facility [Line Items]
Revolving Credit Facility, basis spread on variable rate	0.25%
Maximum
Line of Credit Facility [Line Items]
Ratio of Debt to EBITDA to Increase Revolving Commitment	2.50
Ratio of Debt to EBITDA	4.5
Maximum | Revolving Credit Facility
Line of Credit Facility [Line Items]
Revolving Credit Facility, unused capacity, commitment fee percentage	0.45%
Revolving Credit Facility, letter of credit participation fee percentage	2.00%
Maximum | London Interbank Offered Rate (LIBOR) [Member] | Revolving Credit Facility
Line of Credit Facility [Line Items]
Revolving Credit Facility, basis spread on variable rate	2.00%
Maximum | Base Rate [Member] | Revolving Credit Facility
Line of Credit Facility [Line Items]
Revolving Credit Facility, basis spread on variable rate	1.00%
Revolving Credit Facility, Borrowings At Base Rate Plus LIBOR [Member]
Line of Credit Facility [Line Items]
Interest Expense, Debt		1,900,000
Revolving Credit Facility
Line of Credit Facility [Line Items]
Interest Expense, Debt		2,100,000
Amortization of debt issuance costs		100,000	$ 100,000
Revolving Credit Facility, 31 Day Borrowing | Revolving Credit Facility
Line of Credit Facility [Line Items]
Long-term Debt, Current Maturities		105,000,000
Revolving Credit Facility, 32 Day Borrowing | Revolving Credit Facility
Line of Credit Facility [Line Items]
Long-term Debt, Current Maturities		$ 80,000,000