4. Acquired Intangible Assets and Liabilities

During the year ended December 31, 2012, through the acquisition of DE1 and DE2, the Company added $2.9 million of new intangible assets and $0.2 million of new intangible liabilities with a weighted average life of 4.4 years and 0.5 years, respectively. The Company did not add new intangible assets or liabilities during the year ended December 31, 2011. During the year ended December 31, 2010, the Company added approximately $82.1 million of new intangible assets (excluding amounts attributed to goodwill) and $15.7 million of new intangible liabilities with a weighted average of 3.2 years and 10.8 years, respectively.

The gross above-market and below-market lease value at December 31, 2012, was $6.8 million and $18.6 million, respectively, and total accumulated amortization at December 31, 2012, was $4.5 million and $10.1 million, respectively. The gross above-market and below-market lease value at December 31, 2011, was $8.7 million and $21.1 million, respectively, and total accumulated amortization at December 31, 2012, was $4.3 million and $9.3 million, respectively. The net effect of amortization of acquired above-market and below-market leases resulted in an increase to rental income of $1.5 million, $1.7 million, $0.4 million and $0.2 million, for the years ended December 31, 2012 and 2011, the period from September 28, 2010 to December 31, 2010, and the period from January 1, 2010 to September 27, 2010, respectively. The estimated amortization of acquired below-market leases, net of acquired above-market leases for each of the five succeeding fiscal years, which will be a net increase to rental revenue, is as follows (in thousands):

Year Ending December 31,
2013	$	758
2014	488
2015	544
2016	561
2017	592
Thereafter	3,211
Total	$	6,154

Amortization of all other identified intangible assets was $18.1 million, $32.2 million, $11.1 million and $0.7 million, for the years ended December 31, 2012 and 2011, the period from September 28, 2010 to December 31, 2010, and the period from January 1, 2010 to September 27, 2010, respectively. At December 31, 2012 and 2011, the gross intangible value was $45.7 million and $61.6 million, respectively, and the total accumulated amortization balance was $28.6 million and $29.5 million, respectively. The estimated amortization of all other identified intangible assets for each of the five succeeding fiscal years is as follows (in thousands):

Year Ending December 31,
2013	$	7,405
2014	3,153
2015	2,071
2016	1,664
2017	1,174
Thereafter	1,601
Total	$	17,068