Quarterly Financial Information (unaudited) (Tables)

12 Months Ended

Dec. 31, 2019

Quarterly Financial Information Disclosure [Abstract]

Schedule of Quarterly Financial Information

The following table contains selected financial information from unaudited statements of income for each quarter of 2019 and 2018:

	Quarters Ended
	2019								2018
	Dec. 31		Sept. 30		June 30		Mar. 31		Dec. 31		Sept. 30		June 30		Mar. 31
Revenues	$	288,837	$	275,400	$	275,124	$	247,066	$	241,981	$	236,067	$	236,060	$	221,174
Gross profit	142,275		130,717		127,860		116,048		115,871		111,626		109,276		102,805
Income before income taxes	47,790		40,552		36,419		35,077		40,107		38,626		37,700		39,437
Net income	46,790		40,390		31,999		27,348		31,552		38,924		39,161		37,825
Earnings per diluted share	$	1.15	$	1.00	$	0.80	$	0.69	$	0.79	$	0.96	$	0.97	$	0.95
Shares used in computing diluted    earnings per share	40,736		40,280		39,813		39,585		39,891		40,528		40,224		39,836