Goodwill and Intangible Assets

The following table summarizes the changes in goodwill by operating segment ($ in millions):



	Managed Care		Specialty Services		Total
Balance as of December 31, 2016	$	4,015	$	697	$	4,712
Acquisitions and purchase accounting adjustments	—		37		37
Balance as of December 31, 2017	4,015		734		4,749
Acquisitions and purchase accounting adjustments	1,671		595		2,266
Balance as of December 31, 2018	$	5,686	$	1,329	$	7,015

The majority of the increase in the managed care segment goodwill was related to the acquisition and fair value allocations discussed in Note 3. Fidelis Care Acquisition. The majority of the increase in the specialty services segment goodwill related to other acquisitions discussed in Note 11. Stockholders' Equity.

Intangible assets at December 31, consist of the following ($ in millions):



							Weighted Average Life in Years
	2018			2017			2018	2017
Purchased contract rights	$	1,173		$	1,173		12.6	12.6
Provider contracts	311			274			12.3	11.9
Customer relationships	769			22			10.9	8.2
Trade names	361			162			15.2	9.6
Developed technologies	180			109			5.2	5.0
Other Intangibles	5			7			2.7	2.8
Intangible assets	2,799			1,747			11.9	11.6
Less accumulated amortization:
Purchased contract rights	(283		)	(188		)
Provider contracts	(90		)	(66		)
Customer relationships	(57		)	(21		)
Trade names	(55		)	(34		)
Developed technologies	(72		)	(40		)
Other Intangibles	(3		)	—
Total accumulated amortization	(560		)	(349		)
Intangible assets, net	$	2,239		$	1,398

Amortization expense was $211 million, $156 million and $147 million for the years ended December 31, 2018, 2017 and 2016, respectively. Estimated total amortization expense related to intangible assets for each of the five succeeding fiscal years is as follows ($ in millions):



Year	Expense
2019	$	252
2020	244
2021	223
2022	217
2023	214