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Shareholders' equity (Tables)

9 Months Ended

Sep. 30, 2015

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 nine months ended September 30, 2015 and 2014.

Common and Preferred Stock Activity:	Preferred stock			Common stock
(in shares)	Series A convertible			Treasury		Outstanding
Beginning balance as of December 31, 2014	78,141			4,786,521		89,064,582
Repurchase of common stock	—			2,400,000		(2,400,000	)
Conversion of convertible preferred stock	(1,146	)		—		114,524
Issuance for share-based compensation plans	—			—		152,597
Ending balance as of September 30, 2015	76,995			7,186,521		86,931,703
Beginning balance as of December 31, 2013	79,620			4,786,521		88,710,277
Conversion of convertible preferred stock	(950	)		—		95,039
Issuance for share-based compensation plans	—			—		132,554
Ending balance as of September 30, 2014	78,670			4,786,521		88,937,870

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

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