Consolidated Statement Of Cash Flows (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Cash Flows from Operating Activities
Net income	$ 22,278	$ 20,445
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	7,922	7,354
Deferred income taxes	(681)	(3,397)
Provision for uncollectible accounts receivable	2,967	2,245
Amortization of discount on convertible notes	2,114	1,975
Stock option expense	1,491	1,938
Noncash long-term incentive compensation	612
Changes in operating assets and liabilities, excluding amounts acquired in business combinations:
Increase in accounts receivable	(36,706)	(34,949)
Decrease in inventories	499	200
Decrease in prepaid expenses	(1,092)	1,833
Decrease in accounts payable and other current liabilities	(698)	(3,894)
Increase in income taxes	10,139	15,532
Increase in other assets	(3,071)	(3,654)
Increase in other liabilities	3,282	5,241
Excess tax benefit on share-based compensation	(1,891)	(797)
Other sources	976	309
Net cash provided by operating activities	8,141	10,381
Cash Flows from Investing Activities
Capital expenditures	(5,406)	(12,018)
Business combinations, net of cash acquired		(415)
Other sources	78	311
Net cash used by investing activities	(5,328)	(12,122)
Cash Flows from Financing Activities
Dividends paid	(3,367)	(3,072)
Capital stock surrendered to pay taxes on stock-based compensation	(3,389)	(1,431)
Proceeds from exercise of stock options	10,168	1,042
Excess tax benefit on share-based compensation	1,891	797
Increase/(decrease) in cash overdrafts payable	(3,165)	226
Debt issuance costs	(1,107)
Other sources/(uses)	(419)	312
Net cash provided/(used) by financing activities	612	(2,126)
Increase/(Decrease) in Cash and Cash Equivalents	3,425	(3,867)
Cash and cash equivalents at beginning of year	69,531	38,081
Cash and cash equivalents at end of period	$ 72,956	$ 34,214