FAIR VALUE MEASUREMENTS (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016	Dec. 31, 2014
Interest rate swap agreement
Assets measured at fair value on a recurring basis
Initial notional amount			$ 250,000
Other Observable Inputs (Level 2) | Variable-rate debt
Assets measured at fair value on a recurring basis
Liabilities fair value disclosure	$ 277,000
Recurring
Assets measured at fair value on a recurring basis
Assets fair value disclosure	5,805	$ 5,787
Liabilities fair value disclosure	2,677	3,198
Recurring | Interest rate swap agreement
Assets measured at fair value on a recurring basis
Liabilities fair value disclosure	2,677	3,198
Recurring | Fixed-income securities
Assets measured at fair value on a recurring basis
Assets fair value disclosure	4,074	4,080
Recurring | Money market funds
Assets measured at fair value on a recurring basis
Assets fair value disclosure	1,731	1,707
Recurring | Quoted Prices in Active Markets (Level 1)
Assets measured at fair value on a recurring basis
Assets fair value disclosure	2,737	2,314
Recurring | Quoted Prices in Active Markets (Level 1) | Fixed-income securities
Assets measured at fair value on a recurring basis
Assets fair value disclosure	1,006	607
Recurring | Quoted Prices in Active Markets (Level 1) | Money market funds
Assets measured at fair value on a recurring basis
Assets fair value disclosure	1,731	1,707
Recurring | Other Observable Inputs (Level 2)
Assets measured at fair value on a recurring basis
Assets fair value disclosure	3,068	3,473
Liabilities fair value disclosure	2,677	3,198
Recurring | Other Observable Inputs (Level 2) | Interest rate swap agreement
Assets measured at fair value on a recurring basis
Liabilities fair value disclosure	2,677	3,198
Recurring | Other Observable Inputs (Level 2) | Fixed-income securities
Assets measured at fair value on a recurring basis
Assets fair value disclosure	$ 3,068	$ 3,473