Acquisitions and Divestitures - Divestitures (Details) $ in Millions	1 Months Ended			3 Months Ended			12 Months Ended
	Oct. 31, 2017 USD ($)	Jun. 30, 2017 USD ($)	Jan. 31, 2017 USD ($)	Dec. 31, 2017 USD ($)	Jun. 30, 2017 USD ($) item	Mar. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Sep. 30, 2017 USD ($)
Maximum
Divestiture Information
Aggregate operating income of divested businesses							$ 20
Disposal Group, Held-for-sale, Not Discontinued Operations
Divestiture Information
Disposal - Accounts receivable							25
Disposal - Property, plant and equipment							25
Disposal - Intangible assets							35
Disposal - Deferred revenue							35
Disposal - Goodwill							270	$ 50
Identity Management Business | Disposal Group, Disposed of by Sale, Not Discontinued Operations
Divestiture Information
Annual sales of divested business							$ 205
Safety Prescription Eyewear Business | Disposal Group, Disposed of by Sale, Not Discontinued Operations
Divestiture Information
Annual sales of divested business			$ 45
Pre-tax gain on sale						$ 29
Identity Management and Tolling and Automated License Number Plate Recognition Business in Aggregate | Disposal Group, Disposed of by Sale, Not Discontinued Operations
Divestiture Information
Number of businesses sold | item					2
Proceeds from divested businesses					$ 833
Proceeds from divested businesses, net of cash sold					809
Pre-tax gain on sale					$ 461
Tolling and Automated License Number Plate Recognition Business | Disposal Group, Disposed of by Sale, Not Discontinued Operations
Divestiture Information
Annual sales of divested business		$ 40
Electronic Monitoring Business | Disposal Group, Held-for-sale, Not Discontinued Operations | Estimated Financial Impact
Divestiture Information
Annual sales of divested business	$ 95
Aggregate selling price relative to the divestiture transaction	$ 200
Pre-tax gain on sale				$ 100