GOODWILL AND OTHER INTANGIBLE ASSETS (Tables)

12 Months Ended

Dec. 31, 2017

The balances and changes in the carrying amount of Goodwill by segment are as follows (in thousands of dollars):



Cumulative goodwill impairment charges, January 1, 2017	$	17,038	$	32,265	$	70,299	$	119,602
Impairment	7,169		—		—		7,169
Cumulative goodwill impairment charges, December 31, 2017	$	24,207	$	32,265	$	70,299	$	126,771

e balances and changes in Intangible assets - net are as follows (in thousands of dollars):



		As of December 31,
		2017						2016
	Weighted average life	Gross carrying amount		Accumulated amortization		Net carrying amount		Gross carrying amount		Accumulated amortization		Net carrying amount
Customer lists and relationships	13.8 years	$	430,026	$	195,842	$	234,184	$	424,405	$	175,112	$	249,293
Trademarks, trade names and other	13.5 years	25,886		16,054		9,832		25,353		14,262		11,091
Non-amortized trade names and other		137,491		—		137,491		128,282		—		128,282
Capitalized software	4.1 years	632,431		444,823		187,608		571,978		374,518		197,460
Total intangible assets	8.2 years	$	1,225,834	$	656,719	$	569,115	$	1,150,018	$	563,892	$	586,126

stimated amortization expense for future periods is as follows (in thousands of dollars):