Nature of Operations and Basis of Presentation - Components of Other (Income) Expense, Net (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Other components of net periodic benefit cost	$ (9)	$ (8)
Other (income) expense, net	(4)	(9)
CARE Ratings Limited
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Investments	49		$ 54
Accounting Standards Update 2017-07
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Other components of net periodic benefit cost	(8)	(9)
Loss from investments	4	0
Other (income) expense, net	$ (4)	$ (9)