Consolidated Statements Of Cash Flows (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012
Cash flow from operating activities:
Net income	$ 33,021	$ 45,083
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	33,555	27,316
Stock-based compensation	14,006	13,285
Tax benefit from deferred income taxes	(3,633)	6,695
Tax benefit from stock option plans	(2,042)	(2,094)
Changes in operating assets and liabilities:
Accounts receivable	14,358	(31,203)
Inventories	(14,732)	(16,994)
Prepaid expenses and other assets	(18,418)	(17,625)
Accounts payable	(10,612)	10,596
Deferred revenue	5,097	17,911
Taxes, accrued expenses and other liabilities	(6,208)	(11,169)
Net cash provided by operating activities	44,392	41,801
Cash flow from investing activities:
Capital expenditures	(33,147)	(28,934)
Capitalization of internally developed software	(8,073)	(9,664)
Additions to other intangibles	(2,710)	(1,085)
Purchases of short-term investments	(16,039)	(38,879)
Sales and maturities of short-term investments	35,234	183,058
Net cash (used in) provided by investing activities	(24,735)	104,496
Cash flow from financing activities:
Proceeds from issuance of common stock	20,612	14,422
Dividends paid	(34,727)	(34,019)
Tax benefit from stock option plans	2,042	2,094
Net cash used in financing activities	(12,073)	(17,503)
Net change in cash and cash equivalents	7,584	128,794
Cash and cash equivalents at beginning of period	161,996	142,608
Cash and cash equivalents at end of period	$ 169,580	$ 271,402