Summary of Securities (Detail) - USD ($) $ in Millions	Jun. 26, 2016	Dec. 27, 2015
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Fair Value	$ 2.1
Short-Term Available for Sale
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Amortized Cost	0.1	$ 0.2
Gross Unrealized Losses	0.0	0.0
Fair Value	0.1	0.2
Short-Term Available for Sale \| U.S. Treasury Securities and Obligations of U.S. Government Agencies
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Amortized Cost	0.1	0.2
Gross Unrealized Losses	0.0	0.0
Fair Value	0.1	0.2
Long-Term Available for Sale
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Amortized Cost	1.8	1.8
Gross Unrealized Gains	0.2	0.2
Gross Unrealized Losses	0.0	0.0
Fair Value	2.0	2.0
Long-Term Available for Sale \| U.S. Treasury Securities and Obligations of U.S. Government Agencies
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Amortized Cost	1.7	1.7
Gross Unrealized Gains	0.2	0.2
Gross Unrealized Losses	0.0	0.0
Fair Value	1.9	1.9
Long-Term Available for Sale \| Corporate Debt Securities
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Amortized Cost	0.1	0.1
Gross Unrealized Losses	0.0	0.0
Fair Value	$ 0.1	$ 0.1

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 25
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Reference 2: http://www.xbrl.org/2003/role/presentationRef
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Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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