FAIR VALUE MEASUREMENT (Details) - USD ($) $ in Thousands | Sep. 30, 2018 | Dec. 31, 2017 | Oct. 01, 2017 | Jan. 01, 2017 |
Fair Value Measurement [Line Items] | | | | |
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents | $ 87,441 | $ 73,831 | $ 94,845 | $ 103,222 |
Deferred compensation mutual funds | 25,410 | 22,428 | | |
Restricted investments classified as held-to-maturity | 160,238 | 172,238 | | |
Municipal debt securities | | | | |
Fair Value Measurement [Line Items] | | | | |
Restricted investments classified as held-to-maturity | 76,234 | 83,366 | | |
Corporate debt securities | | | | |
Fair Value Measurement [Line Items] | | | | |
Restricted investments classified as held-to-maturity | 80,194 | 83,791 | | |
Agency mortgage-backed securities | | | | |
Fair Value Measurement [Line Items] | | | | |
Restricted investments classified as held-to-maturity | 2,846 | 4,062 | | |
U.S. government and agency securities | | | | |
Fair Value Measurement [Line Items] | | | | |
Restricted investments classified as held-to-maturity | 964 | 1,019 | | |
Total Fair Value | | | | |
Fair Value Measurement [Line Items] | | | | |
Cash and cash equivalents | 34,736 | 28,780 | | |
Total Fair Value | Restricted Assets | | | | |
Fair Value Measurement [Line Items] | | | | |
Restricted cash and cash equivalents | 52,705 | 45,051 | | |
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents | 87,441 | 73,831 | | |
Deferred compensation mutual funds | 25,410 | 22,428 | | |
Restricted investments classified as held-to-maturity | 160,238 | 172,238 | | |
Total Fair Value | Restricted Assets | Municipal debt securities | | | | |
Fair Value Measurement [Line Items] | | | | |
Restricted investments classified as held-to-maturity | 76,234 | 83,366 | | |
Total Fair Value | Restricted Assets | Corporate debt securities | | | | |
Fair Value Measurement [Line Items] | | | | |
Restricted investments classified as held-to-maturity | 80,194 | 83,791 | | |
Total Fair Value | Restricted Assets | Agency mortgage-backed securities | | | | |
Fair Value Measurement [Line Items] | | | | |
Restricted investments classified as held-to-maturity | 2,846 | 4,062 | | |
Total Fair Value | Restricted Assets | U.S. government and agency securities | | | | |
Fair Value Measurement [Line Items] | | | | |
Restricted investments classified as held-to-maturity | 964 | 1,019 | | |
Quoted Prices in Active Markets for Identical Assets (Level 1) | | | | |
Fair Value Measurement [Line Items] | | | | |
Cash and cash equivalents | 34,736 | 28,780 | | |
Quoted Prices in Active Markets for Identical Assets (Level 1) | Restricted Assets | | | | |
Fair Value Measurement [Line Items] | | | | |
Restricted cash and cash equivalents | 52,705 | 45,051 | | |
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents | 87,441 | 73,831 | | |
Deferred compensation mutual funds | 25,410 | 22,428 | | |
Restricted investments classified as held-to-maturity | 0 | 0 | | |
Quoted Prices in Active Markets for Identical Assets (Level 1) | Restricted Assets | Municipal debt securities | | | | |
Fair Value Measurement [Line Items] | | | | |
Restricted investments classified as held-to-maturity | 0 | 0 | | |
Quoted Prices in Active Markets for Identical Assets (Level 1) | Restricted Assets | Corporate debt securities | | | | |
Fair Value Measurement [Line Items] | | | | |
Restricted investments classified as held-to-maturity | 0 | 0 | | |
Quoted Prices in Active Markets for Identical Assets (Level 1) | Restricted Assets | Agency mortgage-backed securities | | | | |
Fair Value Measurement [Line Items] | | | | |
Restricted investments classified as held-to-maturity | 0 | 0 | | |
Quoted Prices in Active Markets for Identical Assets (Level 1) | Restricted Assets | U.S. government and agency securities | | | | |
Fair Value Measurement [Line Items] | | | | |
Restricted investments classified as held-to-maturity | 0 | 0 | | |
Significant Other Observable Inputs (Level 2) | | | | |
Fair Value Measurement [Line Items] | | | | |
Cash and cash equivalents | 0 | 0 | | |
Significant Other Observable Inputs (Level 2) | Restricted Assets | | | | |
Fair Value Measurement [Line Items] | | | | |
Restricted cash and cash equivalents | 0 | 0 | | |
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents | 0 | 0 | | |
Deferred compensation mutual funds | 0 | 0 | | |
Restricted investments classified as held-to-maturity | 160,238 | 172,238 | | |
Significant Other Observable Inputs (Level 2) | Restricted Assets | Municipal debt securities | | | | |
Fair Value Measurement [Line Items] | | | | |
Restricted investments classified as held-to-maturity | 76,234 | 83,366 | | |
Significant Other Observable Inputs (Level 2) | Restricted Assets | Corporate debt securities | | | | |
Fair Value Measurement [Line Items] | | | | |
Restricted investments classified as held-to-maturity | 80,194 | 83,791 | | |
Significant Other Observable Inputs (Level 2) | Restricted Assets | Agency mortgage-backed securities | | | | |
Fair Value Measurement [Line Items] | | | | |
Restricted investments classified as held-to-maturity | 2,846 | 4,062 | | |
Significant Other Observable Inputs (Level 2) | Restricted Assets | U.S. government and agency securities | | | | |
Fair Value Measurement [Line Items] | | | | |
Restricted investments classified as held-to-maturity | 964 | 1,019 | | |
Significant Unobservable Inputs (Level 3) | | | | |
Fair Value Measurement [Line Items] | | | | |
Cash and cash equivalents | 0 | 0 | | |
Significant Unobservable Inputs (Level 3) | Restricted Assets | | | | |
Fair Value Measurement [Line Items] | | | | |
Restricted cash and cash equivalents | 0 | 0 | | |
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents | 0 | 0 | | |
Deferred compensation mutual funds | 0 | 0 | | |
Restricted investments classified as held-to-maturity | 0 | 0 | | |
Significant Unobservable Inputs (Level 3) | Restricted Assets | Municipal debt securities | | | | |
Fair Value Measurement [Line Items] | | | | |
Restricted investments classified as held-to-maturity | 0 | 0 | | |
Significant Unobservable Inputs (Level 3) | Restricted Assets | Corporate debt securities | | | | |
Fair Value Measurement [Line Items] | | | | |
Restricted investments classified as held-to-maturity | 0 | 0 | | |
Significant Unobservable Inputs (Level 3) | Restricted Assets | Agency mortgage-backed securities | | | | |
Fair Value Measurement [Line Items] | | | | |
Restricted investments classified as held-to-maturity | 0 | 0 | | |
Significant Unobservable Inputs (Level 3) | Restricted Assets | U.S. government and agency securities | | | | |
Fair Value Measurement [Line Items] | | | | |
Restricted investments classified as held-to-maturity | $ 0 | $ 0 | | |