Segment and Related Information - Revenue by Major Customers (Details)	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Revenue, Major Customer [Line Items]
Concentration risk, percentage	100.00%	100.00%	100.00%	100.00%
Operating segments | Restaurant/Retail | McDonald’s Corporation
Revenue, Major Customer [Line Items]
Concentration risk, percentage	22.00%	36.00%	25.00%	40.00%
Operating segments | Restaurant/Retail | Yum! Brands, Inc.
Revenue, Major Customer [Line Items]
Concentration risk, percentage	12.00%	14.00%	12.00%	13.00%
Operating segments | Government | U.S. Department of Defense
Revenue, Major Customer [Line Items]
Concentration risk, percentage	34.00%	23.00%	31.00%	23.00%
Other
Revenue, Major Customer [Line Items]
Concentration risk, percentage	32.00%	27.00%	32.00%	24.00%