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Shareholders' equity (Tables)

9 Months Ended

Sep. 30, 2018

Stockholders' Equity Note [Abstract]

Common and Preferred Stock Activity

The Common and Preferred Stock table below contains additional information about preferred stock conversions during the nine months ended September 30, 2018 and 2017.

	Preferred stock			Common stock
Common and Preferred Stock Activity (in shares):	Series A convertible			Treasury			Outstanding
Beginning balance as of December 31, 2017	74,364			7,186,521			87,544,777
Conversion of convertible preferred stock	(272	)		—			27,263
Issuance for share-based compensation plans	—			—			36,266
Ending balance as of September 30, 2018	74,092			7,186,521			87,608,306
Beginning balance as of December 31, 2016	75,625			7,186,521			87,250,897
Conversion of convertible preferred stock	(326	)		—			32,619
Issuance for share-based compensation plans	—			—			43,436
Ending balance as of September 30, 2017	75,299			7,186,521			87,326,952

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Tabular disclosure of the change in preferred stock, treasury stock and common stock outstanding.

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