9.	Goodwill and Other Intangible Assets

The following table summarizes the changes in the carrying amount of goodwill for the years ended December 31, 2017 and 2016 (dollars in thousands):

										Global
							Asia			Investment			Development
	Americas			EMEA			Pacific			Management			Services			Total
Balance as of December 31, 2015
Goodwill	$	2,260,076		$	1,172,150		$	155,875		$	479,739		$	86,663		$	4,154,503
Accumulated impairment losses		(798,290	)		(138,631	)		—			(44,922	)		(86,663	)		(1,068,506	)
		1,461,786			1,033,519			155,875			434,817			—			3,085,997
Purchase accounting entries related to acquisitions		42,080			36,929			(3,922	)		350			—			75,437
Foreign exchange movement		773			(161,784	)		(1,247	)		(17,784	)		—			(180,042	)
Balance as of December 31, 2016
Goodwill		2,302,929			1,047,295			150,706			462,305			86,663			4,049,898
Accumulated impairment losses		(798,290	)		(138,631	)		—			(44,922	)		(86,663	)		(1,068,506	)
		1,504,639			908,664			150,706			417,383			—			2,981,392
Purchase accounting entries related to acquisitions		104,654			17,402			4,198			17,568			—			143,822
Foreign exchange movement		993			91,761			11,204			25,568			—			129,526
Balance as of December 31, 2017
Goodwill		2,408,576			1,156,458			166,108			505,441			86,663			4,323,246
Accumulated impairment losses		(798,290	)		(138,631	)		—			(44,922	)		(86,663	)		(1,068,506	)
	$	1,610,286		$	1,017,827		$	166,108		$	460,519		$	—		$	3,254,740

During 2017, we completed 11 in-fill acquisitions, including two leading Software as a Service (SaaS) platforms – one that produces scalable interactive visualization technologies for commercial real estate and one that provides technology solutions for facilities management operations, a healthcare-focused project manager in Australia, a full-service brokerage and management boutique in South Florida, a technology-enabled national boutique commercial real estate finance and consulting firm in the United States, a retail consultancy in France, a majority interest in a Toronto-based investment management business specializing in private infrastructure and private equity investments, a San Francisco-based technology-focused boutique real estate brokerage firm, a project management and design engineering firm operating across the United States, a Washington, D.C.-based retail brokerage operation and a leading technical engineering services provider in Italy. During 2016, we acquired our independent affiliate in Norway, a London-based retail property advisor specializing in the luxury goods retail sector and a leading provider of retail project management, shopping center development and tenant coordination services in the U.S.

Our annual assessment of goodwill and other intangible assets deemed to have indefinite lives has historically been completed as of the beginning of the fourth quarter of each year. We performed the 2017, 2016 and 2015 assessments as of October 1. When we performed our required annual goodwill impairment review as of October 1, 2017, 2016 and 2015, we determined that no impairment existed as the estimated fair value of our reporting units was in excess of their carrying value.

Other intangible assets totaled $1.4 billion, net of accumulated amortization of $1.0 billion as of December 31, 2017, and $1.4 billion, net of accumulated amortization of $771.7 million, as of December 31, 2017 and 2016, respectively, and are comprised of the following (dollars in thousands):

	December 31,
	2017					2016
	Gross					Gross
	Carrying		Accumulated			Carrying		Accumulated
	Amount		Amortization			Amount		Amortization
Unamortizable intangible assets
Management contracts	$	90,503				$	101,355
Trademarks		56,800					56,800
Trade names		16,250					18,100
	$	163,553				$	176,255
Amortizable intangible assets
Customer relationships	$	802,597	$	(355,642	)	$	761,290	$	(270,447	)
Mortgage servicing rights		608,757		(235,626	)		501,087		(180,563	)
Trademarks/Trade name		321,406		(64,866	)		306,559		(46,837	)
Management contracts		203,291		(122,450	)		177,014		(99,733	)
Covenant not to compete		73,750		(57,358	)		73,750		(32,777	)
Other		226,496		(164,796	)		186,757		(141,316	)
	$	2,236,297	$	(1,000,738	)	$	2,006,457	$	(771,673	)
Total intangible assets	$	2,399,850	$	(1,000,738	)	$	2,182,712	$	(771,673	)

Unamortizable intangible assets include management contracts identified as a result of the REIM Acquisitions relating to relationships with open-end funds, a trademark separately identified as a result of the 2001 Acquisition and a trade name separately identified in connection with the REIM Acquisitions, which represents the Clarion Partners trade name in the U.S. These intangible assets have indefinite useful lives and accordingly are not being amortized.

Customer relationships relate to existing relationships mainly in the brokerage, occupier outsourcing and property management lines of business that were primarily identified in the Trammell Crow Company Acquisition, the Norland Acquisition and the GWS Acquisition. These intangible assets are being amortized over useful lives of up to 20 years.

Mortgage servicing rights represent the carrying value of servicing assets in our mortgage brokerage line of business in the U.S. The mortgage servicing rights are being amortized over the estimated period that net servicing income is expected to be received, which is typically up to ten years.

In connection with the GWS Acquisition, trademarks of approximately $280 million were separately identified and are being amortized over 20 years.

Management contracts consist primarily of asset management contracts relating to relationships with closed-end funds and separate accounts in the U.S., Europe and Asia that were separately identified as a result of the REIM Acquisitions. These management contracts are being amortized over useful lives of up to 13 years.

A covenant not to compete of approximately $74 million was separately identified in connection with the GWS Acquisition and is being amortized over three years.

Other amortizable intangible assets mainly represent transition costs, which get amortized as a reduction of revenue over the life of the associated contract.

Amortization expense related to intangible assets was $238.7 million, $211.7 million and $175.3 million for the years ended December 31, 2017, 2016 and 2015, respectively. The estimated annual amortization expense for each of the years ending December 31, 2018 through December 31, 2022 approximates $216.2 million, $165.0 million, $138.2 million, $117.0 million and $107.1 million, respectively.