Intangible assets

12 Months Ended

Dec. 31, 2020

Intangible assets

Intangible Assets

18.   Intangible assets

			Accumulated
As at December 31, 2020	Cost		amortization		Net book value
Trade names and trademarks	$	53,871	$	(1,595)	$	52,276
Customer relationships		196,407		(47,752)		148,655
Software and technology assets		206,829		(108,127)		98,702
Software under development		1,315		—		1,315
	$	458,422	$	(157,474)	$	300,948

			Accumulated
As at December 31, 2019	Cost		amortization		Net book value
Trade names and trademarks	$	53,319	$	(2,028)	$	51,291
Customer relationships		124,865		(34,666)		90,199
Software and technology assets		157,776		(78,330)		79,446
Software under development		12,444		—		12,444
	$	348,404	$	(115,024)	$	233,380

At December 31, 2020, a net carrying amount of $51,864,000 (December 31, 2019: $62,589,000) included in intangible assets was not subject to amortization. During the year ended December 31, 2020, the cost of additions was reduced by $2,639,000 for recognition of tax credits (2019: $1,022,000; 2018: $1,606,000).

During the year ended December 31, 2020, interest of $299,000 (2019: $402,000; 2018: $460,000) was capitalized to the cost of software under development. These interest costs relating to qualifying assets are capitalized at a weighted average rate of 3.04% (2019: 4.01%; 2018: 4.09%).

During the year ended December 31, 2020, the weighted average amortization period for all classes of intangible assets was 9.1 years (2019: 7.8; 2018: 8.2 years).

18.   Intangible assets (continued)

As at December 31, 2020, estimated annual amortization expense for the next five years ended December 31 are as follows:

2021	$	45,996
2022		39,561
2023		27,825
2024		19,087
2025		11,322
	$	143,791