Consolidated Statements Of Cash Flows (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Cash flow from operating activities:
Net income	$ 18,600	$ 18,642
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	16,829	14,115
Stock-based compensation	7,134	6,303
Tax benefit from deferred income taxes	(1,902)	(1,567)
Tax benefit from stock option plans	(459)	(246)
Changes in operating assets and liabilities:
Accounts receivable	15,115	1,671
Inventories	(18,045)	(8,413)
Prepaid expenses and other assets	(12,969)	9,468
Accounts payable	1,603	518
Deferred revenue	3,776	5,374
Taxes, accrued expenses and other liabilities	(9,200)	(12,361)
Net cash provided by operating activities	20,482	33,504
Cash flow from investing activities:
Capital expenditures	(19,094)	(9,054)
Capitalization of internally developed software	(2,803)	(3,740)
Additions to other intangibles	(1,418)	(333)
Purchases of short-term investments	(8,177)
Sales and maturities of short-term investments	26,092	84,608
Net cash (used in) provided by investing activities	(5,400)	71,481
Cash flow from financing activities:
Proceeds from issuance of common stock	11,798	7,605
Dividends paid	(17,281)	(16,934)
Tax benefit from stock option plans	459	246
Net cash used by financing activities	(5,024)	(9,083)
Net change in cash and cash equivalents	10,058	95,902
Cash and cash equivalents at beginning of period	161,996	142,608
Cash and cash equivalents at end of period	$ 172,054	$ 238,510