Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Current Assets
Cash and cash equivalents	$ 52,815	$ 58,298
Short-term investments	89,160	105,760
Accounts receivable, less allowance for doubtful accounts of $133 and $130 at March 31, 2014 and December 31, 2013, respectively	100,524	85,814
Other receivables	28,967	18,249
Inventory	87,396	90,111
Prepaid expenses	5,005	4,325
Deferred tax assets, net	15,181	17,083
Total Current Assets	379,048	379,640
Property, plant and equipment, net	75,885	76,739
Deferred tax assets, net	11,491	9,622
Goodwill	3,492	3,492
Other assets	11,933	11,180
Long-term investments	309,452	309,225
Total Assets	791,301	789,898
Current Liabilities
Accounts payable	59,097	48,282
Unearned revenue	27,533	22,205
Accrued expenses	10,683	12,776
Accrued wages and benefits	17,448	14,040
Income tax payable, net	5,272	5,002
Total Current Liabilities	120,033	102,305
Non-current unearned revenue	15,116	14,643
Other non-current liabilities	23,476	22,144
Bonds payable	30,000	46,200
Total Liabilities	188,625	185,292
Commitments and contingencies (see Note 14)
Stockholders' Equity
Common stock, par value $0.01 per share; 200,000 shares authorized; 79,652 shares issued and 56,646 shares outstanding at March 31, 2014 and 79,652 shares issued and 56,918 shares outstanding at December 31, 2013	797	797
Additional paid-in capital	235,624	233,511
Accumulated other comprehensive income	10,084	10,753
Retained earnings	888,121	884,451
Less treasury stock at cost: 23,006 and 22,734 shares at March 31, 2014 and December 31, 2013, respectively	(531,950)	(524,906)
Total Stockholders' Equity	602,676	604,606
Total Liabilities and Stockholders' Equity	$ 791,301	$ 789,898