Consolidated Statements Of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014
Cash flow from operating activities:
Net income	$ 63,124	$ 82,948
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	55,157	51,011
Stock-based compensation	19,151	19,531
Tax benefit from deferred income taxes	(7,404)	2,222
Tax benefit from stock option plans	(944)	(1,189)
Changes in operating assets and liabilities:
Accounts receivable	17,162	(7,046)
Inventories	(14,809)	1,247
Prepaid expenses and other assets	(3,370)	(24,887)
Accounts payable	(5,609)	5,279
Deferred revenue	(1,591)	8,709
Taxes, accrued expenses and other liabilities	(386)	2,891
Net cash provided by operating activities	120,481	140,716
Cash flow from investing activities:
Capital expenditures	(28,102)	(30,645)
Capitalization of internally developed software	(22,639)	(22,055)
Additions to other intangibles	(2,240)	(2,238)
Acquisition, net of cash received	(28,629)
Purchases of short-term investments	(29,649)	(107,664)
Sales and maturities of short-term investments	44,752	82,514
Net cash used in investing activities	(66,507)	(80,088)
Cash flow from financing activities:
Proceeds from revolving line of credit	42,000
Principal payments on revolving line of credit	(17,000)
Proceeds from issuance of common stock	21,252	24,483
Repurchase of common stock	(72,559)
Dividends paid	(73,406)	(57,108)
Tax benefit from stock option plans	944	1,189
Net cash used in financing activities	(98,769)	(31,436)
Net change in cash and cash equivalents	(44,795)	29,192
Cash and cash equivalents at beginning of period	274,030	230,263
Cash and cash equivalents at end of period	$ 229,235	$ 259,455