PARTNERS' EQUITY (Details) (USD $) In Millions, unless otherwise specified	2 Months Ended	9 Months Ended	2 Months Ended	9 Months Ended	1 Months Ended	2 Months Ended		1 Months Ended
	Sep. 30, 2014 TC PipeLines GP, Inc. General Partner	Sep. 30, 2014 TC PipeLines GP, Inc. General Partner	Sep. 30, 2014 ATM Equity Issuance	Sep. 30, 2014 ATM Equity Issuance	Aug. 31, 2014 ATM Equity Issuance Limited Partners Institution	Sep. 30, 2014 ATM Equity Issuance Limited Partners	Sep. 30, 2014 ATM Equity Issuance General Partner	Aug. 31, 2014 ATM Equity Issuance Maximum Expected Limited Partners	Aug. 31, 2014 ATM Equity Issuance Minimum Limited Partners Institution
Partners' Equity
Number of financial institutions					5
Gross proceeds from sale of common units								$ 200
Number of managers to agree with equity sale method									1
Units sold						1.3
Net proceeds from equity issuance			73	73			1
Limited Liability Company (LLC) or Limited Partnership (LP), Managing Member or General Partner, Ownership Interest	2.00%	2.00%
Sales agent commissions						$ 1