Nature of Business and Significant Accounting Policies (Details Textual) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accumulated Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Net of Tax	$ (113,012)	$ (164,643)
Gains and (losses) netted against other income, net	(200)	(2,200)	$ (2,500)
Other Inventory, Demo, Gross	37,600	36,900
Advertising costs	19,200	19,300	$ 18,700
Carrying value of cost-basis investments	$ 3,069	$ 3,200
Effect of stock-based compensation awards, shares excluded for purposes of diluted earnings per share	39,000	233,000	354,000
Unrecognized stock-based compensation costs, net of estimated forfeitures	$ 42,000
Weighted average period of unrecognized stock-based compensation costs, net of estimated forfeitures	2 years 33 days
Estimated forfeiture rate	5.00%
Net cash provided by operating activities	$ 308,252	$ 319,751	$ 293,425
Net cash (used) provided by financing activities	(132,612)	31,136	(184,149)
Excess Tax Benefit from Share-based Compensation, Financing Activities	$ (10,731)	(5,991)	$ (7,032)
Weighted Average Number Diluted Shares Outstanding Adjustment	492,000
Employee Service Share-based Compensation, Tax Benefit from Compensation Expense	$ 4,500
Level 1
Cash equivalents at fair value	$ 140,700	$ 8,300
Time-vested restricted stock unit
Restricted stock units granted	773,000	865,000	804,000
Time-vested and performance-based restricted stock unit
Weighted average grant date fair value per share	$ 36.20	$ 29.48	$ 26.30
Performance-based restricted stock unit [Domain]
Total fair value of awards granted	$ 9,900	$ 1,600
Restricted Stock Unit Awards
Total fair value of awards granted	$ 37,906	$ 28,603	$ 27,150
Market-based restricted stock unit
Restricted stock units granted		64,000	128,000
Weighted average grant date fair value per share		$ 22.89	$ 25.55
Total fair value of awards granted		$ 1,500
Performance-based restricted stock unit [Member]
Restricted stock units granted	283,000	62,000
Weighted average grant date fair value per share	$ 35.08	$ 26.41
Stock Option Awards
Cash received from the exercise of stock options	$ 53,500	$ 7,700	$ 20,800
Employee Service Share-based Compensation, Tax Benefit from Exercise of Stock Options	$ 3,000	1,300	3,900
ASU 2016-09 adjustment effect
Net cash provided by operating activities		6,000	9,400
Net cash (used) provided by financing activities		(6,000)	(9,400)
Excess Tax Benefit from Share-based Compensation, Financing Activities		$ (1,500)	$ (8,200)