COMMITMENTS AND CONTINGENCIES - Workers' Compensation Commitments (Details) (USD $)	9 Months Ended
	Sep. 26, 2014		Dec. 27, 2013
Workers' Compensation Commitments [Line Items]
Cash collateral held by insurance carriers	$ 22,643,000		$ 23,747,000
Cash and cash equivalents held in Trust	25,806,000	[1]	31,474,000	[1]
Investments held in Trust	92,699,000		86,678,000
Letters of credit	22,573,000	[2]	7,867,000	[2]
Surety bonds	15,742,000	[3]	16,099,000	[3]
Total collateral commitments	179,463,000		165,865,000
Accrued interest on trust investments	900,000		800,000
Cash collateral backing letters of credit	$ 1,864,000		$ 1,864,000
Surety bonds annual fee limit, % of bond amount	2.00%
Surety bonds required cancellation notice	60 days
Minimum
Workers' Compensation Commitments [Line Items]
Surety bonds review and renewal period if elected	1 year
Maximum [Member]
Workers' Compensation Commitments [Line Items]
Surety bonds review and renewal period if elected	4 years

[1] Included in this amount is $0.9 million and $0.8 million of accrued interest at September 26, 2014 and December 27, 2013, respectively.

[2] We have agreements with certain financial institutions to issue letters of credit as collateral. We had $1.9 million of restricted cash collateralizing our letters of credit at September 26, 2014 and December 27, 2013, respectively.

[3] Our surety bonds are issued by independent insurance companies on our behalf and bear annual fees based on a percentage of the bond, which is determined by each independent surety carrier. These fees do not exceed 2.0% of the bond amount, subject to a minimum charge. The terms of these bonds are subject to review and renewal every one to four years and most bonds can be canceled by the sureties with as little as 60 days notice.