Correction of an Error (Details) $ in Thousands		3 Months Ended		6 Months Ended
		Jul. 01, 2017 USD ($)		Jul. 01, 2017 USD ($)		Apr. 01, 2017 USD ($)	Dec. 31, 2016 USD ($)
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Temporary Equity, Other Changes		$ 4,711		$ 4,711
Number of put option periods				2
Duration of put option periods				60 days
Retained earnings	[1]	138,468		$ 138,468			$ 133,951
Redeemable common shares related to 401KSOP and Employee Stock Ownership Plan (ESOP)		123,169		123,169			124,201
Common shares		36,183	[1]	36,183	[1]	$ 36,183	35,857	[1]
Additional paid-in capital	[1]	52,514		52,514			41,626
Scenario, Previously Reported [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Retained earnings		299,521		299,521			290,292
Redeemable common shares related to 401KSOP and Employee Stock Ownership Plan (ESOP)		0		0			0
Common shares						42,914	42,914
Additional paid-in capital		7,899		7,899			2,429
Temporary equity [Member] | Restatement Adjustment [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Retained earnings		(143,902)		(143,902)			(139,190)
Redeemable common shares related to 401KSOP and Employee Stock Ownership Plan (ESOP)		123,169		123,169			124,201
Common shares						(2,425)	(2,751)
Additional paid-in capital		23,158		23,158			17,740
Stock split [Member] | Restatement Adjustment [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Retained earnings		(17,151)		(17,151)			(17,151)
Redeemable common shares related to 401KSOP and Employee Stock Ownership Plan (ESOP)		0		0			0
Common shares						$ (4,306)	(4,306)
Additional paid-in capital		$ 21,457		$ 21,457			$ 21,457

[1] Adjusted for two-for-one stock split