Segment Information - Schedule of consolidated non-current assets by geographic area (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-lived assets, including operating lease ROU assets	$ 1,599	$ 1,550
U.S.
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-lived assets, including operating lease ROU assets	681	686
Americas other than U.S.
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-lived assets, including operating lease ROU assets	127	145
United Kingdom
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-lived assets, including operating lease ROU assets	213	225
Ireland
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-lived assets, including operating lease ROU assets	11	10
Other Europe, Middle East, & Africa
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-lived assets, including operating lease ROU assets	357	309
Asia Pacific
Revenues from External Customers and Long-Lived Assets [Line Items]
Long-lived assets, including operating lease ROU assets	$ 210	$ 175