Consolidated Statement Of Cash Flows (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011
Cash Flows from Operating Activities
Net income	$ 41,719	$ 38,387
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	14,861	14,755
Deferred income taxes	(4,895)	(18)
Provision for uncollectible accounts receivable	4,730	4,365
Amortization of discount on convertible notes	3,985	3,724
Stock option expense	4,312	4,495
Noncash long-term incentive compensation		2,595
Changes in operating assets and liabilities, excluding amounts acquired in business combinations:
Increase in accounts receivable	(8,543)	(9,271)
Decrease/(increase) in inventories	522	(954)
Decrease/(increase) in prepaid expenses	672	(59)
Decrease in accounts payable and other current liabilities	(3,593)	(6,603)
Increase/(decrease) in income taxes	(1,029)	3,738
Increase in other assets	(2,283)	(5,652)
Increase in other liabilities	4,493	4,514
Excess tax benefit on share-based compensation	(1,069)	(3,339)
Other sources	773	450
Net cash provided by operating activities	54,655	51,127
Cash Flows from Investing Activities
Capital expenditures	(18,474)	(14,960)
Business combinations, net of cash acquired	(1,500)	(3,689)
Other sources/(uses)	357	(869)
Net cash used by investing activities	(19,617)	(19,518)
Cash Flows from Financing Activities
Dividends paid	(6,160)	(5,967)
Purchases of treasury stock	(12,841)	(25,482)
Proceeds from issuance of capital stock	3,670	7,698
Excess tax benefit on share-based compensation	1,069	3,339
Increase/(decrease) in cash overdrafts payable	985	(7,814)
Debt issuance costs		(2,723)
Other sources	124	364
Net cash used by financing activities	(13,153)	(30,585)
Increase in Cash and Cash Equivalents	21,885	1,024
Cash and cash equivalents at beginning of year	38,081	49,917
Cash and cash equivalents at end of period	$ 59,966	$ 50,941