7.	Intangible Assets and Liabilities

The following summarizes our intangible assets (acquired above-market leases and acquired in-place leases) and intangible liabilities (acquired below-market leases) as of March 31, 2017 and December 31, 2016.

	As of
(Amounts in thousands)	March 31, 2017			December 31, 2016
Intangible assets:
Gross amount	$	560,809		$	579,066
Accumulated amortization		(171,221	)		(166,841	)
	$	389,588		$	412,225
Intangible liabilities:
Gross amount	$	203,674		$	208,367
Accumulated amortization		(58,536	)		(55,349	)
	$	145,138		$	153,018

Amortization of acquired below-market leases, net of acquired above-market leases, resulted in an increase to rental income of $3,008,000 for the three months ended March 31, 2017 and a decrease to rental income of $3,619,000 for the three months ended March 31, 2016. The three months ended March 31, 2016 included $9,834,000 of expense, from the write-off of an above-market lease asset in connection with the termination of a tenant’s lease and $3,915,000 of income from the acceleration of a below-market lease liability in connection with a tenant’s lease modification. Estimated annual amortization of acquired below-market leases, net of acquired above-market leases, for each of the five succeeding years commencing January 1, 2018 is as follows.

(Amounts in thousands)
2018	$	14,220
2019		12,010
2020		9,625
2021		4,546
2022		1,181

Amortization of acquired in-place leases (a component of depreciation and amortization expense) was $17,774,000 and $30,692,000 for the three months ended March 31, 2017 and 2016, respectively. Estimated annual amortization of acquired in-place leases for each of the five succeeding years commencing January 1, 2018 is as follows.

(Amounts in thousands)
2018	$	54,581
2019		48,184
2020		41,073
2021		28,268
2022		23,654