(9) Intangibles

The Company's intangible lease assets were (in thousands):

	December 31,

Intangible lease assets	2013			2012
Lease-up intangibles	$	578,143		$	580,319
Above market tenant lease intangibles		144,355			153,141
Below market ground lease intangibles		58,939			58,939

Gross intangible lease assets		781,437			792,399
Accumulated depreciation and amortization		(291,595	)		(240,662	)

Net intangible lease assets	$	489,842		$	551,737

The remaining weighted average amortization period of intangible assets was 15 years at both December 31, 2013 and 2012.

The Company's intangible lease liabilities were (in thousands):

	December 31,

Intangible lease liabilities	2013			2012
Below market lease intangibles	$	201,234		$	188,534
Above market ground lease intangibles		6,121			6,091

Gross intangible lease liabilities		207,355			194,625
Accumulated depreciation and amortization		(108,545	)		(90,445	)

Net intangible lease liabilities	$	98,810		$	104,180

The remaining weighted average amortization period of unfavorable market lease intangibles was approximately nine years at both December 31, 2013 and 2012.

In 2013, the Company restated the above weighted average amortization periods of intangible assets and liabilities as of December 31, 2012, which were previously reported as 12 years and 8 years, respectively.

For the years ended December 31, 2013, 2012 and 2011, rental income includes additional revenues of $9 million, $4 million and $6 million, respectively, from the amortization of net below market lease intangibles. For the years ended December 31, 2013, 2012 and 2011, operating expenses include additional expense of $0.8 million, $0.7 million and $0.6 million, respectively, from the amortization of net above market ground lease intangibles. For the years ended December 31, 2013, 2012 and 2011, depreciation and amortization expense includes additional expense of $59 million, $44 million and $45 million, respectively, from the amortization of lease-up and non-compete agreement intangibles.

Estimated aggregate amortization of intangible assets and liabilities for each of the five succeeding fiscal years and thereafter follows (in thousands):

	Intangible Assets		Intangible Liabilities

2014	$	69,556	$	16,728
2015		65,639		16,171
2016		61,395		15,643
2017		53,847		13,674
2018		41,791		11,290
Thereafter		197,614		25,304

	$	489,842	$	98,810