Consolidated Statements Of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014
Cash flow from operating activities:
Net income	$ 39,946	$ 43,246
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	36,502	33,357
Stock-based compensation	12,745	12,881
Tax benefit from deferred income taxes	(1,561)	1,398
Tax benefit from stock option plans	(937)	(1,055)
Changes in operating assets and liabilities:
Accounts receivable	(2,748)	(30,140)
Inventories	(12,228)	4,815
Prepaid expenses and other assets	(19,544)	(25,942)
Accounts payable	(2,082)	7,368
Deferred revenue	3,692	10,499
Taxes, accrued expenses and other liabilities	(3,002)	12,011
Net cash provided by operating activities	50,783	68,438
Cash flow from investing activities:
Capital expenditures	(20,626)	(22,109)
Capitalization of internally developed software	(11,446)	(16,797)
Additions to other intangibles	(520)	(1,634)
Acquisition, net of cash received	(24,523)
Purchases of short-term investments	(29,649)	(80,515)
Sales and maturities of short-term investments	36,796	79,647
Net cash used in investing activities	(49,968)	(41,408)
Cash flow from financing activities:
Proceeds from issuance of common stock	14,416	17,124
Repurchase of common stock	(8,545)
Dividends paid	(48,869)	(37,976)
Tax benefit from stock option plans	937	1,055
Net cash used in financing activities	(42,061)	(19,797)
Net change in cash and cash equivalents	(41,246)	7,233
Cash and cash equivalents at beginning of period	274,030	230,263
Cash and cash equivalents at end of period	$ 232,784	$ 237,496