Impact on the entity's income tax provision of the Tax Cuts and Jobs Act of 2017.

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The aggregate cost of goods produced and sold and services rendered during the reporting period.

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Amount after tax of increase (decrease) to equity or (increase) decrease to net assets, resulting from the cumulative effect adjustment of a new accounting principle applied in the period of adoption.

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The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

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Represents the quantification of the effect of adopting the new accounting standard or change in accounting principle expected by the entity to have a significant effect on the entity's financial statements.

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The aggregate amount of income or expense from ancillary business-related activities (that is to say, excluding major activities considered part of the normal operations of the business).

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The aggregate total costs related to selling a firm's product and services, as well as all other general and administrative expenses. Direct selling expenses (for example, credit, warranty, and advertising) are expenses that can be directly linked to the sale of specific products. Indirect selling expenses are expenses that cannot be directly linked to the sale of specific products, for example telephone expenses, Internet, and postal charges. General and administrative expenses include salaries of non-sales personnel, rent, utilities, communication, etc.

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New accounting pronouncements (impact of other adoptions) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Jan. 01, 2018
Total cost of revenue	$ (190,201)	$ (179,368)	$ (378,959)	$ (358,682)
Selling, general and administrative expense	(209,585)	(208,656)	(420,739)	(425,800)
Operating income	82,823	92,827	170,531	177,825
Other income	2,436	1,250	3,724	2,312
Net income	60,207	59,579	123,544	116,645
Product [Member]
Total cost of revenue	(134,332)	(130,728)	(267,703)	(263,260)
Service [Member]
Total cost of revenue	(55,869)	(48,640)	(111,256)	(95,422)
Retained earnings [Member]
Net income			123,544
Accounting Standards Update No. 2016-01 [Member]
Adoption of new accounting pronouncement			0
Accounting Standards Update No. 2016-16 [Member] \| Retained earnings [Member]
Adoption of new accounting pronouncement					$ 0
Adoption of Accounting Standards Update No. 2018-02 [Member]
Adoption of new accounting pronouncement	0		0
Adoption of Accounting Standards Update No. 2018-02 [Member] \| Retained earnings [Member]
Adoption of new accounting pronouncement	6,867		6,867
Adoption of Accounting Standards Update No. 2018-02 [Member] \| Accumulated other comprehensive loss [Member]
Adoption of new accounting pronouncement	(6,867)		(6,867)
Accounting Standards Update No. 2018-05 [Member]
Impact of Tax Cuts and Jobs Act of 2017	$ 441		$ 131
As previously reported [Member] \| Accounting Standards Update No. 2017-07 [Member]
Total cost of revenue		(179,214)		(358,374)
Selling, general and administrative expense		(208,306)		(425,100)
Operating income		93,331		178,833
Other income		746		1,304
Net income		59,579		116,645
As previously reported [Member] \| Accounting Standards Update No. 2017-07 [Member] \| Product [Member]
Total cost of revenue		(130,591)		(262,986)
As previously reported [Member] \| Accounting Standards Update No. 2017-07 [Member] \| Service [Member]
Total cost of revenue		(48,623)		(95,388)
Effect of adoption [Member] \| Accounting Standards Update No. 2017-07 [Member]
Total cost of revenue		(154)		(308)
Selling, general and administrative expense		(350)		(700)
Operating income		(504)		(1,008)
Other income		504		1,008
Net income		0		0
Effect of adoption [Member] \| Accounting Standards Update No. 2017-07 [Member] \| Product [Member]
Total cost of revenue		(137)		(274)
Effect of adoption [Member] \| Accounting Standards Update No. 2017-07 [Member] \| Service [Member]
Total cost of revenue		$ (17)		$ (34)