Year Ended December 31,

2021

2020

2019

(Dollars in thousands, except per share amounts)

Numerator

Net income

$

573,657

$

367,582

$

238,312

Less: distributed earnings allocated to participating securities

(634)

(583)

(466)

Less: undistributed earnings allocated to participating securities

(2,343)

(1,748)

(1,020)

Net income attributable to common stockholders (numerator for basic earnings per share)

570,680

365,251

236,826

Add back: undistributed earnings allocated to participating securities

2,343

1,748

1,020

Less: undistributed earnings reallocated to participating securities

(2,269)

(1,704)

(992)

Numerator for diluted earnings per share under two class method

$

570,754

$

365,295

$

236,854

Denominator

Weighted-average common shares outstanding

70,174,281

68,531,856

66,546,347

Add: dilutive effect of stock options

2,302,773

1,792,006

1,876,980

Add: dilutive effect of contingently issuable equity awards

377,547

352,719

375,552

Denominator for diluted earnings per share under two class method

72,854,601

70,676,581

68,798,879

Basic Earnings Per Common Share

$

8.13

$

5.33

$

3.56

Diluted Earnings Per Common Share

$

7.83

$

5.17

$

3.44