Regulatory and Rate Matters Regulatory and Rate Matters (Tables)

12 Months Ended

Dec. 31, 2015

Regulated Operations [Abstract]

Schedule of Rate Increases for Transmission Costs

Effective Date	Aggregate Collection Amount		Performance Bonus
	(in millions)
January 1, 2013	$	5.2	$	—
March 1, 2014	5.6		0.7
March 1, 2015	5.7		1.5
March 1, 2016	6.0		0.7

The following sets forth TNMP’s recent interim transmission cost rate increases:

Effective Date	Approved Increase in Rate Base		Annual Increase in Revenue
	(in millions)
September 27, 2012	$	26.4	$	2.5
March 20, 2013	21.9		2.9
September 17, 2013	18.1		2.8
March 13, 2014	18.2		2.9
September 8, 2014	25.2		4.2
March 16, 2015	27.1		4.4
September 10, 2015	7.0		1.4