Revenue - Estimated Minimum Revenue Expected to be Recognized in Future Related to Unsatisfied Performance Obligations (Details) $ in Millions	Mar. 31, 2018 USD ($)
Revenue From Contract With Customer [Abstract]
Fixed consideration to be recognized, 2018	$ 322.1
Fixed consideration to be recognized, 2019	368.1
Fixed consideration to be recognized, 2020 and after	$ 1,400.0

Fixed consideration related to unsatisfied performance obligations expected to be recognized in third year and thereafter.

No definition available.

Name:	trgp_FixedConsiderationRelatedToUnsatisfiedPerformanceObligationsExpectedToBeRecognizedInThirdYearAndThereafter
Namespace Prefix:	trgp_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant