Debt - Schedule of redemption prices plus accrued and unpaid interest (Details) - Unsecured debt			3 Months Ended
	Feb. 09, 2018	Feb. 08, 2018	Mar. 30, 2019
Debt Instrument, Redemption [Line Items]
Redemption price (as a percent)			101.00%
Dollar Senior Note redemption price
Debt Instrument, Redemption [Line Items]
Redemption price (as a percent)	103.00%	103.00%
Dollar Senior Note redemption price | During the year commencing July 15, 2018
Debt Instrument, Redemption [Line Items]
Redemption price (as a percent)			101.50%
Dollar Senior Note redemption price | During the year commencing July 15, 2019 and thereafter
Debt Instrument, Redemption [Line Items]
Redemption price (as a percent)			100.00%