Basic and diluted earnings per common share were calculated as follows (in thousands, except per share amounts):
Three Months Ended September 30,
Nine Months Ended September 30,
2018
2017
2018
2017
Basic weighted average number of shares outstanding
40,283
40,323
40,472
40,273
Effect of dilutive securities:
Convertible debt (1)
—
1,105
—
1,754
Unvested restricted stock
572
583
628
558
Diluted average shares outstanding
40,855
42,011
41,100
42,585
Net earnings as reported
$
54,135
$
42,550
$
151,847
$
107,702
Interest attributable to Convertible Notes, net of income taxes (1)
—
201
—
942
Net earnings for diluted earnings per share
$
54,135
$
42,751
$
151,847
$
108,644
Basic earnings per share
$
1.34
$
1.06
$
3.75
$
2.67
Diluted earnings per share (1)
$
1.33
$
1.02
$
3.69
$
2.55
Antidilutive stock not included in the calculation of diluted earnings per share
—
2
1
4
(1)
In accordance with ASC 260-10, Earnings Per Share, ("ASC 260-10") we calculate the dilutive effect of convertible securities using the "if-converted" method based on the number of days our Convertible Notes were outstanding during the period. All of the Convertible Notes were retired in the second half of 2017.