Quarterly Results (unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Quarterly Financial Information Disclosure [Abstract]
Total revenues	$ 469,240	$ 356,976	$ 330,984	$ 332,393	$ 405,588	$ 344,141	$ 322,432	$ 299,893	$ 1,489,593	$ 1,372,054	$ 1,207,295
Gross profit	409,213	301,154	274,182	273,262	341,260	282,425	262,166	248,880	1,257,811	1,134,731	1,006,221
Net income	$ 58,088	$ 60,883	$ 38,101	$ (6,404)	$ 123,023	$ 30,745	$ 32,589	$ 32,449	$ 150,668	$ 218,806	$ 128,687
Net income per common share:
Basic (in dollars per share)	$ 1.30	$ 1.31	$ 0.81	$ (0.13)	$ 2.54	$ 0.63	$ 0.67	$ 0.67	$ 3.24	$ 4.52	$ 2.64
Diluted (in dollars per share)	$ 1.27	$ 1.31	$ 0.80	$ (0.13)	$ 2.45	$ 0.62	$ 0.66	$ 0.66	$ 3.18	$ 4.39	$ 2.59
Weighted average shares outstanding
Basic (in shares)	44,504,222	46,279,515	46,850,944	47,620,774	47,626,833	47,673,211	47,727,786	47,560,749	46,308,825	47,647,397	47,950,746
Diluted (in shares)	45,642,292	46,309,072	47,437,555	47,620,774	49,425,395	49,064,272	49,102,879	48,509,181	47,122,511	49,025,684	48,927,791