Segment Disclosures and Related Information - Net Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Net Income (Loss) Attributable to ConocoPhillips [Abstract]
Consolidated net income (loss) attributable to ConocoPhillips	$ 982	$ (1,739)
Assets [Abstract]
Assets	83,693		$ 62,618
Alaska [Member] \| Operating Segments [Member]
Net Income (Loss) Attributable to ConocoPhillips [Abstract]
Consolidated net income (loss) attributable to ConocoPhillips	159	81
Assets [Abstract]
Assets	14,571		14,623
Lower 48 [Member] \| Operating Segments [Member]
Net Income (Loss) Attributable to ConocoPhillips [Abstract]
Consolidated net income (loss) attributable to ConocoPhillips	468	(437)
Assets [Abstract]
Assets	32,474		11,932
Canada [Member] \| Operating Segments [Member]
Net Income (Loss) Attributable to ConocoPhillips [Abstract]
Consolidated net income (loss) attributable to ConocoPhillips	10	(109)
Assets [Abstract]
Assets	6,925		6,863
Europe, Middle East And North Africa [Member] \| Operating Segments [Member]
Net Income (Loss) Attributable to ConocoPhillips [Abstract]
Consolidated net income (loss) attributable to ConocoPhillips	153	201
Assets [Abstract]
Assets	8,689		8,756
Asia Pacific [Member] \| Operating Segments [Member]
Net Income (Loss) Attributable to ConocoPhillips [Abstract]
Consolidated net income (loss) attributable to ConocoPhillips	317	272
Assets [Abstract]
Assets	11,041		11,231
Other International [Member] \| Operating Segments [Member]
Net Income (Loss) Attributable to ConocoPhillips [Abstract]
Consolidated net income (loss) attributable to ConocoPhillips	(4)	28
Assets [Abstract]
Assets	229		226
Corporate and Other [Member] \| Corporate, Non-Segment [Member]
Net Income (Loss) Attributable to ConocoPhillips [Abstract]
Consolidated net income (loss) attributable to ConocoPhillips	(121)	$ (1,775)
Assets [Abstract]
Assets	$ 9,764		$ 8,987