v3.7.0.1
Fair Value Measurements - Assets and Liabilities Measured on a Recurring Basis (Details) - Fair Value, Measurements, Recurring - USD ($)
$ in Thousands
Jul. 01, 2017
Dec. 31, 2016
Assets:    
Total assets $ 35,084 $ 35,014
Money market mutual funds    
Assets:    
Cash and cash equivalents, fair value disclosure 20,084 20,014
Certificates of deposit    
Assets:    
Cash and cash equivalents, fair value disclosure 15,000 15,000
Level 1    
Assets:    
Total assets 35,084 35,014
Level 1 | Money market mutual funds    
Assets:    
Cash and cash equivalents, fair value disclosure 20,084 20,014
Level 1 | Certificates of deposit    
Assets:    
Cash and cash equivalents, fair value disclosure 15,000 15,000
Level 2    
Assets:    
Total assets 0 0
Level 2 | Money market mutual funds    
Assets:    
Cash and cash equivalents, fair value disclosure 0 0
Level 2 | Certificates of deposit    
Assets:    
Cash and cash equivalents, fair value disclosure 0 0
Level 3    
Assets:    
Total assets 0 0
Level 3 | Money market mutual funds    
Assets:    
Cash and cash equivalents, fair value disclosure 0 0
Level 3 | Certificates of deposit    
Assets:    
Cash and cash equivalents, fair value disclosure $ 0 $ 0