Selected Quarterly Financial Data (Unaudited) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017		Dec. 31, 2016		Dec. 31, 2015
Quarterly Financial Information Disclosure [Abstract]
Total revenues	$ 678	$ 673	$ 676	$ 662	$ 642	$ 651	$ 659	$ 643	$ 2,689		$ 2,595		$ 2,673
Profit before income taxes	133	126	164	167	122	146	148	145	590		561		619
Profit	$ 271	$ 86	$ 114	$ 115	$ 85	$ 97	$ 102	$ 100	$ 586	[1]	$ 384	[1]	$ 460	[1]

[1] Profit attributable to Caterpillar Financial Services Corporation.