8.	Intangible Assets and Liabilities

The following table summarizes our intangible assets (acquired above-market leases and acquired in-place leases) and intangible liabilities (acquired below-market leases) as of September 30, 2017 and December 31, 2016.

	As of
(Amounts in thousands)	September 30, 2017			December 31, 2016
Intangible assets:
Gross amount	$	562,262		$	579,066
Accumulated amortization		(189,209	)		(166,841	)
	$	373,053		$	412,225
Intangible liabilities:
Gross amount	$	210,016		$	208,367
Accumulated amortization		(71,453	)		(55,349	)
	$	138,563		$	153,018

Amortization of acquired below-market leases, net of acquired above-market leases, resulted in an increase to “rental income” of $3,175,000 and $3,112,000 for the three months ended September 30, 2017 and 2016, respectively, and $14,164,000 and $6,593,000 for the nine months ended September 30, 2017 and 2016, respectively. The three and nine months ended September 30, 2016 included $1,743,000 and $11,577,000 of expense, respectively, from the write-off of above-market lease assets in connection with lease terminations. 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	$	16,281
2019		14,355
2020		8,750
2021		4,491
2022		1,091

Amortization of acquired in-place leases (a component of “depreciation and amortization” expense) was $17,929,000 and $21,917,000 for the three months ended September 30, 2017 and 2016, respectively, and $58,352,000 and $76,072,000 for the nine months ended September 30, 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	$	60,896
2019		54,639
2020		42,316
2021		30,123
2022		24,009