Unaudited Interim Condensed Consolidated Statements of Operations and Comprehensive Income - USD ($)
$ in Thousands
 3 Months Ended 9 Months Ended 12 Months Ended
Sep. 30, 2021
Sep. 30, 2020
Sep. 30, 2021
Sep. 30, 2020
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Income Statement [Abstract]              
Revenues, net of discounts $ 224,092 $ 136,274 $ 633,037 $ 353,096 $ 521,533 $ 252,819 $ 102,817
Cost of goods sold 70,147 34,097 199,345 86,557 135,116 60,982 22,385
Gross profit 153,945 102,177 433,692 266,539 386,418 191,837 80,431
Expenses:              
Sales and marketing 51,724 30,890 142,858 80,764 119,395 59,349 25,050
General and administrative 28,218 8,502 55,869 22,696 36,056 14,071 19,156
Depreciation and amortization 7,728 3,314 19,829 8,612 12,600 5,079 1,138
Total expenses 87,670 42,706 218,556 112,072 168,051 78,499 45,344
Income from operations 66,275 59,471 215,136 154,467 218,367 113,338 35,088
Other income (expense):              
Interest expense, net (6,145) (5,352) (20,693) (16,566) (20,237) (9,050) (2,103)
Other (expense) income, net 89 (10,756) 385 (10,827) (40,680) (607) 60
Total other expense (6,056) (16,108) (20,308) (27,393) (60,917) (9,658) (2,044)
Income before provision for income taxes 60,219 43,363 194,828 127,074 157,450 103,680 33,044
Provision for income taxes 41,603 25,948 105,254 67,116 94,451 50,586 22,151
Net income and comprehensive income $ 18,616 $ 17,415 $ 89,574 $ 59,958 $ 62,999 $ 53,094 $ 10,893
Basic net income per common share $ 0.15 $ 0.16 $ 0.73 $ 0.54 $ 0.55 $ 0.48 $ 0.11
Diluted net income per common share $ 0.14 $ 0.15 $ 0.68 $ 0.52 $ 0.53 $ 0.46 $ 0.11
Weighted average number of common shares used in computing net income per common share:              
Basic 128,146,298 112,039,640 122,983,729 111,824,816 113,572,379 110,206,103 101,697,002
Diluted 136,909,266 117,949,224 130,927,083 115,998,704 118,325,724 115,317,942 103,201,127