Segment and Related Information - Revenue by Major Customers (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 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	15.00%	23.00%	20.00%	35.00%
Operating segments | Restaurant/Retail | Yum! Brands, Inc.
Revenue, Major Customer [Line Items]
Concentration risk, percentage	13.00%	17.00%	11.00%	14.00%
Operating segments | Government | U.S. Department of Defense
Revenue, Major Customer [Line Items]
Concentration risk, percentage	38.00%	31.00%	33.00%	25.00%
Other
Revenue, Major Customer [Line Items]
Concentration risk, percentage	34.00%	29.00%	36.00%	26.00%