11. Intangible assets

The changes in the carrying value of intangible assets for the year ended March 31, 2018 are as follows:


Gross carrying value	Customer contracts			Customer relationships		Intellectual Property and other rights		Trade names			Technology			Leasehold benefits		Covenant not-to- compete		Service mark		Software		Total
Balance as at April 1, 2017	$	167,001		$	121,922	$	3,861	$	653		$	6,131		$	1,835	$	9,451		400	$	25,586	$	336,840
Additions		—			—		250		—			—			—		—		—		7,369		7,619
Translation adjustments		93			940		470		—			(6	)		—		10		—		894		2,401

Balance as at March 31, 2018	$	167,094		$	122,862	$	4,581	$	653		$	6,125		$	1,835	$	9,461	$	400	$	33,849	$	346,860

Accumulated amortization
Balance as at April 1, 2017	$	157,976		$	62,175	$	3,861	$	80		$	172		$	1,835	$	964	$	—	$	13,153	$	240,216
Amortization		2,725			3,700		74		236			790			—		2,310		—		5,670		15,505
Translation adjustments		(62	)		873		470		(1	)		(4	)		—		12		—		199		1,487

Balance as at March 31, 2018	$	160,639		$	66,748	$	4,405	$	315		$	958		$	1,835	$	3,286	$	—	$	19,022	$	257,208

Net carrying value as at March 31, 2018	$	6,455		$	56,114	$	176	$	338		$	5,167		$	—	$	6,175	$	400	$	14,827	$	89,652

The changes in the carrying value of intangible assets for the year ended March 31, 2019 are as follows:


Gross carrying value	Customer contracts			Customer relationships			Intellectual Property and other rights			Trade names			Technology			Leasehold benefits		Covenant not-to- compete			Service mark		Software			Total
Balance as at April 1, 2018	$	167,094		$	122,862		$	4,581		$	653		$	6,125		$	1,835	$	9,461			400	$	33,849		$	346,860
Additions		—			—			—			—			—			—		—			—		7,556			7,556
Translation adjustments		(5,146	)		(1,225	)		(298	)		(6	)		(73	)		—		(172	)		—		(1,742	)		(8,662	)

Balance as at March 31, 2019	$	161,948		$	121,637		$	4,283		$	647		$	6,052		$	1,835	$	9,289		$	400	$	39,663		$	345,754

Accumulated amortization
Balance as at April 1, 2018	$	160,639		$	66,748		$	4,405		$	315		$	958		$	1,835	$	3,286		$	—	$	19,022		$	257,208
Amortization		2,675			3,671			125			192			776			—		2,240			—		6,104			15,783
Translation adjustments		(4,940	)		(1,031	)		(298	)		(6	)		(17	)		—		(79	)		—		(1,054	)		(7,425	)

Balance as at March 31, 2019	$	158,374		$	69,338		$	4,232		$	501		$	1,717		$	1,835	$	5,447		$	—	$	24,072		$	265,566

Net carrying value as at March 31, 2019	$	3,574		$	52,249		$	51		$	146		$	4,335		$	—	$	3,842		$	400	$	15,591		$	80,188

As at March 31, 2019, the estimated remaining weighted average amortization periods for definite lived intangible assets are as follows:


	Balance life
	(in months)
Customer contracts		19
Customer relationships		196
Covenant not-to-compete		21
Trade names		10
Technology		68
Intellectual property and other rights		5
Software		20

The estimated annual amortization expense based on remaining weighted average amortization periods for intangible assets and exchange rates, each as at March 31, 2019 are as follows:


	Amount
2020	$	15,716
2021		12,078
2022		7,000
2023		5,649
2024		4,398
Thereafter		34,947

	$	79,788	*

*	excludes service mark, as it has an indefinite useful life