Selected Quarterly Financial Data - Unaudited (Tables)

12 Months Ended

Dec. 31, 2020

Quarterly Financial Data - Unaudited [Abstract]

Schedule of Quarterly Financial Information [Table Text Block]

	Quarter Ended
	Mar. 31		Jun. 30		Sept. 30		Dec. 31
	(in thousands except per share data)
2020
Total revenue	$	328,607	$	303,379	$	318,567	$	320,451
Gross profit	$	121,415	$	106,284	$	113,924	$	119,874
Net income	$	16,834	$	18,908	$	24,986	$	26,142
Net income per share:
Basic	$	0.81	$	0.91	$	1.19	$	1.24
Diluted	$	0.78	$	0.88	$	1.16	$	1.21
2019
Total revenue	$	330,932	$	312,282	$	307,471	$	315,523
Gross profit	$	135,303	$	103,869	$	118,552	$	114,140
Net income (loss)	$	30,998	$	22,833	$	26,563	$	20,641
Net income (loss) per share:
Basic	$	1.51	$	1.11	$	1.29	$	1.00
Diluted	$	1.44	$	1.06	$	1.24	$	0.96