FAIR VALUE MEASUREMENT - Fair Value Measurement (Details) - USD ($) $ in Thousands | Jun. 26, 2022 | Dec. 26, 2021 | Jun. 27, 2021 | Dec. 27, 2020 |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | | | |
Cash, cash equivalents, restricted cash and restricted cash equivalents | $ 89,995 | $ 103,185 | $ 159,670 | $ 118,612 |
Restricted investments classified as held-to-maturity | 118,265 | 138,084 | | |
Municipal debt securities | | | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | | | |
Restricted investments classified as held-to-maturity | 52,266 | 58,505 | | |
Corporate debt securities | | | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | | | |
Restricted investments classified as held-to-maturity | 64,928 | 78,357 | | |
Agency mortgage-backed securities | | | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | | | |
Restricted investments classified as held-to-maturity | 85 | 152 | | |
U.S. government and agency securities | | | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | | | |
Restricted investments classified as held-to-maturity | 986 | 1,070 | | |
Fair value, recurring | Total fair value | | | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | | | |
Cash and cash equivalents | 32,432 | 49,896 | | |
Fair value, recurring | Total fair value | Restricted assets | | | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | | | |
Restricted cash and cash equivalents | 57,563 | 53,289 | | |
Cash, cash equivalents, restricted cash and restricted cash equivalents | 89,995 | 103,185 | | |
Restricted investments classified as held-to-maturity | 118,265 | 138,084 | | |
Fair value, recurring | Total fair value | Restricted assets | Municipal debt securities | | | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | | | |
Restricted investments classified as held-to-maturity | 52,266 | 58,505 | | |
Fair value, recurring | Total fair value | Restricted assets | Corporate debt securities | | | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | | | |
Restricted investments classified as held-to-maturity | 64,928 | 78,357 | | |
Fair value, recurring | Total fair value | Restricted assets | Agency mortgage-backed securities | | | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | | | |
Restricted investments classified as held-to-maturity | 85 | 152 | | |
Fair value, recurring | Total fair value | Restricted assets | U.S. government and agency securities | | | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | | | |
Restricted investments classified as held-to-maturity | 986 | 1,070 | | |
Fair value, recurring | Quoted prices in active markets for identical assets (level 1) | | | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | | | |
Cash and cash equivalents | 32,432 | 49,896 | | |
Fair value, recurring | Quoted prices in active markets for identical assets (level 1) | Restricted assets | | | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | | | |
Restricted cash and cash equivalents | 57,563 | 53,289 | | |
Cash, cash equivalents, restricted cash and restricted cash equivalents | 89,995 | 103,185 | | |
Restricted investments classified as held-to-maturity | 0 | 0 | | |
Fair value, recurring | Quoted prices in active markets for identical assets (level 1) | Restricted assets | Municipal debt securities | | | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | | | |
Restricted investments classified as held-to-maturity | 0 | 0 | | |
Fair value, recurring | Quoted prices in active markets for identical assets (level 1) | Restricted assets | Corporate debt securities | | | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | | | |
Restricted investments classified as held-to-maturity | 0 | 0 | | |
Fair value, recurring | Quoted prices in active markets for identical assets (level 1) | Restricted assets | Agency mortgage-backed securities | | | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | | | |
Restricted investments classified as held-to-maturity | 0 | 0 | | |
Fair value, recurring | Quoted prices in active markets for identical assets (level 1) | Restricted assets | U.S. government and agency securities | | | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | | | |
Restricted investments classified as held-to-maturity | 0 | 0 | | |
Fair value, recurring | Significant other observable inputs (level 2) | | | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | | | |
Cash and cash equivalents | 0 | 0 | | |
Fair value, recurring | Significant other observable inputs (level 2) | Restricted assets | | | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | | | |
Restricted cash and cash equivalents | 0 | 0 | | |
Cash, cash equivalents, restricted cash and restricted cash equivalents | 0 | 0 | | |
Restricted investments classified as held-to-maturity | 118,265 | 138,084 | | |
Fair value, recurring | Significant other observable inputs (level 2) | Restricted assets | Municipal debt securities | | | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | | | |
Restricted investments classified as held-to-maturity | 52,266 | 58,505 | | |
Fair value, recurring | Significant other observable inputs (level 2) | Restricted assets | Corporate debt securities | | | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | | | |
Restricted investments classified as held-to-maturity | 64,928 | 78,357 | | |
Fair value, recurring | Significant other observable inputs (level 2) | Restricted assets | Agency mortgage-backed securities | | | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | | | |
Restricted investments classified as held-to-maturity | 85 | 152 | | |
Fair value, recurring | Significant other observable inputs (level 2) | Restricted assets | U.S. government and agency securities | | | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | | | |
Restricted investments classified as held-to-maturity | 986 | 1,070 | | |
Fair value, recurring | Significant unobservable inputs (level 3) | | | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | | | |
Cash and cash equivalents | 0 | 0 | | |
Fair value, recurring | Significant unobservable inputs (level 3) | Restricted assets | | | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | | | |
Restricted cash and cash equivalents | 0 | 0 | | |
Cash, cash equivalents, restricted cash and restricted cash equivalents | 0 | 0 | | |
Restricted investments classified as held-to-maturity | 0 | 0 | | |
Fair value, recurring | Significant unobservable inputs (level 3) | Restricted assets | Municipal debt securities | | | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | | | |
Restricted investments classified as held-to-maturity | 0 | 0 | | |
Fair value, recurring | Significant unobservable inputs (level 3) | Restricted assets | Corporate debt securities | | | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | | | |
Restricted investments classified as held-to-maturity | 0 | 0 | | |
Fair value, recurring | Significant unobservable inputs (level 3) | Restricted assets | Agency mortgage-backed securities | | | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | | | |
Restricted investments classified as held-to-maturity | 0 | 0 | | |
Fair value, recurring | Significant unobservable inputs (level 3) | Restricted assets | U.S. government and agency securities | | | | |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | | | | |
Restricted investments classified as held-to-maturity | $ 0 | $ 0 | | |