	March 31, 2019							December 31, 2018
(In thousands)	Gross Carrying Amount		Accumulated Amortization			Net Carrying Amount		Gross Carrying Amount		Accumulated Amortization			Net Carrying Amount
Deferred financing costs on undrawn revolver	$	1,025	$	(811	)	$	214	$	1,025	$	(779	)	$	246
Other regulatory assets:
Deferred financing costs		10,610		(5,810	)		4,800		10,610		(5,490	)		5,120
Deferred costs recoverable in future years		23,793		—			23,793		23,793		—			23,793
Other regulatory assets		34,403		(5,810	)		28,593		34,403		(5,490	)		28,913
Operating lease right-of-use asset		345		—			345		—		—			—
Investments		2,519		—			2,519		2,519		—			2,519
Other assets	$	38,292	$	(6,621	)	$	31,671	$	37,947	$	(6,269	)	$	31,678

Deferred financing costs on undrawn revolver consist of costs incurred in connection with the establishment of the InfraREIT LP revolving credit facility. See Note 8, Borrowings Under Credit Facilities.

Other regulatory assets consist of deferred financing costs within our regulated subsidiary, SDTS. The deferred financing costs primarily consist of debt issuance costs incurred in connection with the construction of SDTS’s regulated assets or the refinancing of related debt. These assets are classified as regulatory assets and amortized over the length of the related loan. These costs are recovered through rates established in rate cases.

Deferred costs recoverable in future years of $23.8 million at March 31, 2019 and December 31, 2018 represent operating costs incurred from the inception of Sharyland through 2007. We have determined that these costs are probable of recovery through future rates based on orders of the PUCT in Sharyland’s prior rate cases and regulatory precedent.

Operating lease right-of-use asset represents the asset associated with two land leases in which we are the lessee. For additional information see Note 16, Leases.

In connection with the acquisition of Cap Rock Holding Corporation, we received a participation in the National Rural Utilities Cooperative Finance Corporation. We account for this investment under the cost method of accounting. We believe that the investment is not impaired as of March 31, 2019 and December 31, 2018.