Condensed Consolidated Statements Of Income - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Revenues:
Total revenues	$ 273,616	$ 210,116	$ 801,458	$ 622,418
Cost of revenues (1)	42,371	36,992	126,339	106,870
Gross profit	231,245	173,124	675,119	515,548
Operating expenses:
Sales and marketing (1)	79,432	46,425	237,772	143,155
Research, development and engineering (1)	12,431	8,965	35,737	27,165
General and administrative (1)	76,425	55,612	232,118	170,823
Total operating expenses	168,288	111,002	505,627	341,143
Income from operations	62,957	62,122	169,492	174,405
Interest (income) expense, net	25,326	10,436	51,406	30,971
Other (income) expense, net	(3,890)	(9,718)	660	(9,805)
Income before income taxes	41,521	61,404	117,426	153,239
Income tax expense	9,163	15,835	27,872	43,958
Net income	$ 32,358	$ 45,569	$ 89,554	$ 109,281
Net income per common share:
Basic	$ 0.67	$ 0.95	$ 1.86	$ 2.25
Diluted	$ 0.66	$ 0.94	$ 1.81	$ 2.24
Weighted average shares outstanding:
Basic	47,609,819	47,310,011	47,540,593	47,775,798
Diluted	48,521,082	47,494,744	48,745,680	47,997,674
Cash dividends paid per common share	$ 0.3850	$ 0.3450	$ 1.1250	$ 1.0050
Allocated Share-based Compensation Expense	$ 4,563	$ 3,699	$ 13,740	$ 9,947
Cost of Sales [Member]
Allocated Share-based Compensation Expense	120	116	357	314
Selling and Marketing Expense [Member]
Allocated Share-based Compensation Expense	365	423	1,265	1,388
Research and Development Expense [Member]
Allocated Share-based Compensation Expense	296	235	815	663
General and Administrative Expense [Member]
Allocated Share-based Compensation Expense	$ 3,782	$ 2,925	$ 11,303	$ 7,582