Derivative instruments and hedging transactions - Textuals (Details) - USD ($) $ in Millions		12 Months Ended
	Feb. 28, 2014	Dec. 26, 2015	Dec. 27, 2014
Derivative [Line Items]
Other comprehensive income (loss), unrealized gain (loss), before tax	$ 5.8
Derivative, gain			$ 6.2
Interest rate swap
Derivative [Line Items]
Derivative, fair value		$ 5.3
Derivative, gain		1.8
Other current liabilities
Derivative [Line Items]
Interest payable		$ 1.0