Premises and Equipment and Other Assets

Premises and Equipment

Premises and equipment are carried at cost, less accumulated depreciation and amortization. As of December 31, 2017 and 2016, the amounts were as follows:



	December 31,
	2017							2016
(Dollars in millions)	Cost		Accumulated Depreciation and Amortization			Net Book Value		Cost		Accumulated Depreciation and Amortization			Net Book Value
Land	$	119	$	—		$	119	$	120	$	—		$	120
Premises	477		(291		)	186		473		(275		)	198
Leasehold improvements	447		(279		)	168		405		(255		)	150
Furniture, fixtures and equipment	678		(541		)	137		637		(514		)	123
Total	$	1,721	$	(1,111	)	$	610	$	1,635	$	(1,044	)	$	591

Rental, depreciation and amortization expenses were as follows:



	For the Years Ended December 31,
(Dollars in millions)	2017		2016		2015
Rental expense of premises	$	157	$	128	$	134
Less: rental income	5		15		24
Net rental expense	$	152	$	113	$	110
Depreciation and amortization of premises and equipment	$	95	$	92	$	99

Future minimum lease payments at December 31, 2017 were as follows:



(Dollars in millions)	2017
Years ending December 31,:
2018	$	144
2019	130
2020	116
2021	98
2022	66
Thereafter	403
Total minimum lease payments	$	957
Minimum rental income due in the future under subleases	$	6

The Company's leases are for land, branch or office space. A majority of the leases provide for the payment of taxes, maintenance, insurance, and certain other expenses applicable to the leased premises. Many of the leases contain extension provisions and escalation clauses. These leases are generally renewable and may in certain cases contain provisions and options to expand or contract space, renew or terminate the lease or purchase the leased premises at predetermined contractual dates. In addition, escalation clauses may exist, which are tied to either a predetermined rate or may change based on a specified percentage increase or the Consumer Price Index.

At December 31, 2017 and 2016, the Company had a liability of $4 million for asset retirement obligations. These obligations include environmental remediation on buildings and the removal of leasehold improvements from leased premises to be vacated in cases where management has sufficient information to estimate the obligation's fair value.

Other Assets

The following table shows the balances of other assets as of December 31, 2017 and 2016.



(Dollars in millions)	December 31, 2017		December 31, 2016
Other investments	$	3,412	$	3,468
Software	424		441
Intangible assets	377		246
OREO	—		3
Other	4,587		4,338
Total other assets	$	8,800	$	8,496