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Shareholders' equity (Tables)

6 Months Ended

Jun. 30, 2017

Stockholders' Equity Note [Abstract]

Common and Preferred Stock Activity

The Common and Preferred Stock Activity table below contains additional information about preferred stock conversions during the six months ended June 30, 2017 and 2016.

Common and Preferred Stock Activity:	Preferred stock			Common stock
(in shares)	Series A convertible			Treasury		Outstanding
Beginning balance as of December 31, 2016	75,625			7,186,521		87,250,897
Conversion of convertible preferred stock	(279	)		—		27,904
Issuance for share-based compensation plans	—			—		37,164
Ending balance as of June 30, 2017	75,346			7,186,521		87,315,965
Beginning balance as of December 31, 2015	76,539			7,186,521		87,038,050
Conversion of convertible preferred stock	(161	)		—		16,109
Issuance for share-based compensation plans	—			—		21,428
Ending balance as of June 30, 2016	76,378			7,186,521		87,075,587

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

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