Earnings per common share (Details) - $ / shares shares in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Earnings Per Share [Abstract]
Weighted average common shares outstanding - basic	198,270	195,524	197,341	195,415
Effect of dilutive performance share awards and restricted stock units	17	645	15	662
Weighted average common shares outstanding - diluted	198,287	196,169	197,356	196,077
Shares excluded from the calculation of diluted earnings per share	0	0	93	0
Dividends declared per common share	$ 0.2025	$ 0.1975	$ 0.4050	$ 0.3950

Securities (including those issuable pursuant to contingent stock agreements) that could potentially dilute basic earnings per share (EPS) or earnings per unit (EPU) in the future that were not included in the computation of diluted EPS or EPU because to do so would increase EPS or EPU amounts or decrease loss per share or unit amounts for the period presented.

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- Definition

Aggregate dividends declared during the period for each share of common stock outstanding.

+ References

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-Publisher FASB
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- Definition

The sum of dilutive potential common shares or units used in the calculation of the diluted per-share or per-unit computation.

+ References

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- Definition

The average number of shares or units issued and outstanding that are used in calculating diluted EPS or earnings per unit (EPU), determined based on the timing of issuance of shares or units in the period.

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Number of [basic] shares or units, after adjustment for contingently issuable shares or units and other shares or units not deemed outstanding, determined by relating the portion of time within a reporting period that common shares or units have been outstanding to the total time in that period.

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