Nature of Business and Significant Accounting Policies (Details Textual) (USD $) Share data in Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Accumulated Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Net of Tax	$ (61,956,000)	$ 26,506,000
Gains and (losses) netted against other income, net	200,000	(300,000)	(3,000,000)
Carrying value of demonstration units	39,600,000	42,700,000
Advertising costs	12,600,000	10,700,000	8,500,000
Carrying value of cost-basis investments	13,500,000	13,500,000
Effect of stock-based compensation awards, shares excluded for purposes of diluted earnings per share	171	549	1,198
Unrecognized stock-based compensation costs, net of estimated forfeitures	36,000,000
Weighted average period of unrecognized stock-based compensation costs, net of estimated forfeitures	1 year 9 months 18 days
Estimated forfeiture rate	5.00%
Level 1
Cash Equivalents, at Carrying Value	29,800,000	28,500,000
Time-vested restricted stock unit
Restricted stock units granted	685	1,173	985
Time-vested and performance-based restricted stock unit
Weighted average grant date fair value per share	$ 32.80	$ 23.98	$ 21.66
Market-based restricted stock unit
Restricted stock units granted		7	795
Weighted average grant date fair value per share		$ 15.87	$ 11.73
Total fair value of awards granted		100,000
Restricted Stock Unit Awards
Total fair value of awards granted	22,500,000	28,239,000	30,660,000
Market-based restricted stock unit [Member]
Total fair value of awards granted			9,325,000
Stock Option Awards
Weighted average grant date fair value per share	$ 7.41	$ 5.92	$ 6.43
Cash received from the exercise of stock options	44,200,000	4,600,000	3,600,000
Related tax benefit realized from the exercise of the stock options	$ 12,800,000	$ 600,000	$ 100,000