Intangible Assets and Liabilities

The gross carrying amount and accumulated amortization (accretion) of our intangible assets and liabilities, other than goodwill, were as follows:



	March 31, 2018									December 31, 2017
	Gross			Accumulated (Amortization) Accretion			Net			Gross		Accumulated (Amortization) Accretion			Net
	(in thousands)
Intangible Assets
Core-developed technology	$	531,263		$	(423,634	)	$	107,629		$	429,548	$	(399,969	)	$	29,579
Customer contracts and relationships	400,566			(210,757		)	189,809			258,586		(197,582		)	61,004
Trademarks and trade names	82,337			(68,982		)	13,355			70,056		(66,004		)	4,052
Other	11,664			(11,073		)	591			11,661		(11,068		)	593
Total intangible assets subject to amortization	$	1,025,830		$	(714,446	)	$	311,384		$	769,851	$	(674,623	)	$	95,228
In-process research and development	7,600			—			7,600			—		—			—
Total intangible assets	$	1,033,430		$	(714,446	)	$	318,984		$	769,851	$	(674,623	)	$	95,228

Intangible Liabilities
Customer contracts and relationships	$	(23,900	)	$	1,304		$	(22,596	)	$	—	$	—		$	—

A summary of intangible assets and liabilities activity is as follows:



	Three Months Ended March 31,
	2018			2017
	(in thousands)
Beginning balance, intangible assets, gross	$	769,851		$	669,896
Intangible assets acquired	240,600			—
Effect of change in exchange rates	22,979			16,168
Ending balance, intangible assets, gross	$	1,033,430		$	686,064

Beginning balance, intangible liabilities, gross	$	—		$	—
Intangible liabilities acquired	(23,900		)	—
Effect of change in exchange rates	—			—
Ending balance, intangible liabilities, gross	$	(23,900	)	$	—

On January 5, 2018, we completed our acquisition of SSNI by purchasing 100% of the voting stock. Intangible assets acquired in 2018 are based on the preliminary purchase price allocation relating to this acquisition. Acquired intangible assets include in-process research and development (IPR&D), which is not amortized until such time as the associated development projects are completed. Of these projects, $6.8 million were completed during the first quarter of 2018 and are included in core-developed technology. The remaining IPR&D is expected to be completed in the next year. Acquired intangible liabilities reflect the present value of the projected cash outflows for an existing contract where remaining costs are expected to exceed projected revenues. Refer to Note 17 for additional information regarding this acquisition.

Estimated future annual amortization (accretion) is as follows:



Year Ending December 31,	Amortization		Accretion			Estimated Annual Amortization, net
	(in thousands)
2018 (amount remaining at March 31, 2018)	$	58,564	$	(3,913	)	$	54,651
2019	72,345		(8,233		)	64,112
2020	52,265		(8,028		)	44,237
2021	36,649		(1,963		)	34,686
2022	26,317		(459		)	25,858
Beyond 2022	65,244		—			65,244
Total intangible assets subject to amortization (accretion)	$	311,384	$	(22,596	)	$	288,788

We have recognized $17.7 million and $4.5 million of net amortization of intangible assets for the three months ended March 31, 2018 and 2017, respectively, within operating expenses in the Consolidated Statement of Operations. These expenses relate to intangible assets and liabilities acquired as part of a business combination.