CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Total revenues	$ 1,489,593	$ 1,372,054	$ 1,207,295
Cost of revenues	231,782	237,323	201,074
Gross profit	1,257,811	1,134,731	1,006,221
Operating expenses:
Sales and marketing	413,474	379,183	338,304
Research, development and engineering	64,295	54,396	48,370
General and administrative	445,431	424,072	375,267
Total operating expenses	923,200	857,651	761,941
Income from operations	334,611	277,080	244,280
Interest expense, net	131,975	69,546	61,987
Gain on sale of businesses	(17,122)	0	0
Loss on investments, net	20,991	4,211	73
Other (income) expense , net	(31,632)	3,725	4,633
Income before income taxes and net loss in earnings of equity method investment	230,399	199,598	177,587
Income tax expense (benefit)	68,393	(19,376)	44,760
Net loss in earnings of equity method investment	11,338	168	4,140
Net income	$ 150,668	$ 218,806	$ 128,687
Net income per common share:
Basic (in dollars per share)	$ 3.24	$ 4.52	$ 2.64
Diluted (in dollars per share)	$ 3.18	$ 4.39	$ 2.59
Weighted average shares outstanding:
Basic (in shares)	46,308,825	47,647,397	47,950,746
Diluted (in shares)	47,122,511	49,025,684	48,927,791
Cash dividends paid per common share (in dollars per share)	$ 0	$ 0.90	$ 1.68
Share-based compensation expense	$ 24,006	$ 23,922	$ 28,093
Cost of revenues
Weighted average shares outstanding:
Share-based compensation expense	535	525	510
Sales and marketing
Weighted average shares outstanding:
Share-based compensation expense	1,454	1,547	1,798
Research, development and engineering
Weighted average shares outstanding:
Share-based compensation expense	1,779	1,477	1,553
General and administrative
Weighted average shares outstanding:
Share-based compensation expense	$ 20,238	$ 20,373	$ 24,232