Fair Value Measurements Non-Recurring Fair Value Measurements (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jul. 01, 2018	Jul. 02, 2017	Jul. 01, 2018	Jul. 02, 2017	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis
Impairment of Long-Lived Assets Held-for-use	$ 1,603	$ 201	$ 1,768	$ 218
Impairment of Long-Lived Assets to be Disposed of		$ 52	41	$ 545
Fair Value, Measurements, Nonrecurring
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis
Assets Held and Used, Long Lived, Fair Value Disclosure	161		161		$ 757
Assets Held-for-sale, Long Lived, Fair Value Disclosure	427		427		1,560
Total	588		588		2,317
Fair Value, Measurements, Nonrecurring | Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis
Assets Held and Used, Long Lived, Fair Value Disclosure	0		0		0
Assets Held-for-sale, Long Lived, Fair Value Disclosure	0		0		0
Total	0		0		0
Fair Value, Measurements, Nonrecurring | Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis
Assets Held and Used, Long Lived, Fair Value Disclosure	0		0		0
Assets Held-for-sale, Long Lived, Fair Value Disclosure	0		0		0
Total	0		0		0
Fair Value, Measurements, Nonrecurring | Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Nonrecurring Basis
Assets Held and Used, Long Lived, Fair Value Disclosure	161		161		757
Assets Held-for-sale, Long Lived, Fair Value Disclosure	427		427		1,560
Total	$ 588		$ 588		$ 2,317