Consolidated Statements Of Cash Flows (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Cash flow from operating activities:
Net income	$ 15,004	$ 18,723
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	17,924	16,994
Stock-based compensation	6,391	6,553
Tax benefit from deferred income taxes	(2,238)	(3,198)
Tax benefit from stock option plans	(16)	(70)
Changes in operating assets and liabilities:
Accounts receivable	11,828	(865)
Inventories	(2,797)	1,852
Prepaid expenses and other assets	(8,254)	(2,790)
Accounts payable	(1,700)	6,213
Deferred revenue	2,909	5,910
Taxes, accrued expenses and other liabilities	(12,640)	(3,180)
Net cash provided by operating activities	26,411	46,142
Cash flow from investing activities:
Capital expenditures	(10,263)	(11,959)
Capitalization of internally developed software	(2,222)	(7,602)
Additions to other intangibles	(399)	(1,049)
Acquisition, net of cash received	(24,523)
Purchases of short-term investments	(22,332)	(9,649)
Sales and maturities of short-term investments	15,774	3,389
Net cash used in investing activities	(43,965)	(26,870)
Cash flow from financing activities:
Proceeds from issuance of common stock	7,402	10,000
Dividends paid	(24,346)	(18,904)
Tax benefit from stock option plans	16	70
Net cash used in financing activities	(16,928)	(8,834)
Net change in cash and cash equivalents	(34,482)	10,438
Cash and cash equivalents at beginning of period	274,030	230,263
Cash and cash equivalents at end of period	$ 239,548	$ 240,701