Selected Quarterly Financial Data (Unaudited) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018		Dec. 31, 2017		Dec. 31, 2016
Quarterly Financial Information Disclosure [Abstract]
Total revenues	$ 699	$ 735	$ 723	$ 690	$ 678	$ 673	$ 676	$ 662	$ 2,847		$ 2,689		$ 2,595
Profit before income taxes	46	163	100	124	133	126	164	167	433		590		561
Profit	$ 18	$ 125	$ 71	$ 91	$ 271	$ 86	$ 114	$ 115	$ 305	[1]	$ 586	[1]	$ 384	[1]

[1] Profit attributable to Caterpillar Financial Services Corporation.