Accumulated Other Comprehensive Loss - Changes in Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands		3 Months Ended					6 Months Ended
		Mar. 27, 2020	Dec. 27, 2019	Mar. 29, 2019		Dec. 28, 2018	Mar. 27, 2020	Mar. 29, 2019
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period		$ 272,131	$ 232,936	$ 124,155		$ 122,059	$ 232,936	$ 122,059
Other comprehensive loss before reclassifications		(6,229)		952			(1,120)	(1,794)
Amounts reclassified from accumulated other comprehensive loss		226		15			433	40
Total other comprehensive income (loss)		(6,003)	5,316	967		(2,721)	(687)	(1,754)
Reclassification of stranded tax benefits	[1]			0
Balance at end of period		295,434	272,131	158,497		124,155	295,434	158,497
Defined benefit pension items
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period		(23,611)	(23,818)	(6,023)		(6,048)	(23,818)	(6,048)
Other comprehensive loss before reclassifications		0		0			0	0
Amounts reclassified from accumulated other comprehensive loss		226		15			433	40
Total other comprehensive income (loss)		226		15			433	40
Reclassification of stranded tax benefits				(2,333)				(2,333)
Balance at end of period		(23,385)	(23,611)	(8,341)		(6,023)	(23,385)	(8,341)
Currency translation adjustments
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period		(12,771)	(17,880)	(13,136)		(10,390)	(17,880)	(10,390)
Other comprehensive loss before reclassifications		(6,229)		952			(1,120)	(1,794)
Amounts reclassified from accumulated other comprehensive loss		0		0			0	0
Total other comprehensive income (loss)		(6,229)		952			(1,120)	(1,794)
Reclassification of stranded tax benefits				0				0
Balance at end of period		(19,000)	(12,771)	(12,184)		(13,136)	(19,000)	(12,184)
Total
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Balance at beginning of period		(36,382)	(41,698)	(19,159)		(16,438)	(41,698)	(16,438)
Total other comprehensive income (loss)		(6,003)	5,316	967		(2,721)
Reclassification of stranded tax benefits				(2,333)	[1]			(2,333)
Balance at end of period		$ (42,385)	$ (36,382)	$ (20,525)		$ (19,159)	$ (42,385)	$ (20,525)

[1] Due to the adoption of ASU 2018-02.