XML 81 R50.htm IDEA: XBRL DOCUMENT v3.6.0.2
ORGANIZATION - Capitalization (Details) - shares
12 Months Ended
Apr. 01, 2015
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Common units        
Partners' Equity        
Number of units   67,400,000 64,300,000 63,600,000
General Partner | TC PipeLines GP, Inc.        
Partners' Equity        
IDRs ownership (as a percent)   100.00%    
Ownership interest in the Partnership (as a percent) 2.00% 2.00% 2.00% 2.00%
Limited Partners | Common units        
Partners' Equity        
Number of units   67,454,831    
Limited Partners | Common units | TC PipeLines GP, Inc.        
Partners' Equity        
Number of units   5,797,106    
Limited Partners | Common units | TransCanada        
Partners' Equity        
Number of units   11,287,725    
Limited partner interest (as a percent)   25.30%    
Limited Partners | Class B units | TransCanada        
Partners' Equity        
Number of units   1,900,000    
Limited partner interest (as a percent)   100.00%