Other Intangible Assets Other Intangible Assets

12 Months Ended

Dec. 31, 2017

Other Intangible Assets Disclosure [Abstract]

Our identifiable intangible assets are as follows (in thousands):



	Useful			Accumulated
As of December 31, 2017	Life	Gross		Amortization			Net
Intangible assets subject to amortization:
Supply contract	11.5	$	12,227	$	(12,138	)	$	89
Intangible assets not subject to amortization:
Rights-of-way assets	Indefinite	15,828					15,828
Total		$	28,055	$	(12,138	)	$	15,917



	Useful			Accumulated
As of December 31, 2016	Life	Gross		Amortization			Net
Intangible assets subject to amortization:
Supply contract	11.5	$	12,227	$	(11,075	)	$	1,152
Intangible assets not subject to amortization:
Rights-of-way assets	Indefinite	13,268					13,268
Total		$	25,495	$	(11,075	)	$	14,420

Amortization of intangible assets was $1.1 million during each of the years ended December 31, 2017, 2016 and 2015, and is included in depreciation and amortization on the accompanying consolidated statements of income and comprehensive income. Amortization expense is estimated to be $0.1 million for the year ended December 31, 2018, at which point our supply contract will be fully amortized.