CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
OPERATING ACTIVITIES
Net Income	$ 152,149	$ 137,664	$ 123,330
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation, amortization and other non-cash charges	42,139	42,277	39,304
Provision for deferred income taxes	3,493	8,440	356
Stock based compensation expense	12,110	10,579	10,427
Excess tax benefits from share-based payments	(1,946)	(4,744)	(3,722)
Provision for bad debts	10,113	11,197	10,388
Changes in assets and liabilities:
Trade accounts receivables and other accounts receivables	(12,494)	(13,369)	(13,617)
Financed receivables	(3,630)	(941)	(950)
Materials and supplies	814	(1,525)	(118)
Other current assets	(2,144)	(10,678)	(4,613)
Other non-current assets	154	7,200	(1,343)
Accounts payable and accrued expenses	(2,039)	15,273	4,918
Unearned revenue	2,822	2,497	3,561
Accrued insurance	126	1,274	(1,572)
Pension funding	(5,000)	(5,250)	(5,000)
Long-term accrued liabilities	(311)	(5,748)	1,316
Net cash provided by operating activities	196,356	194,146	162,665
INVESTING ACTIVITIES
Cash used for acquisitions of companies, net of cash acquired	(33,462)	(63,335)	(12,632)
Capital expenditures	(39,495)	(28,739)	(18,632)
Cash from sales of franchises	767	565	102
Proceeds from sales of assets	2,752	2,038	372
Investment Tax Credits	(504)
Net cash used in investing activities	(69,942)	(89,471)	(30,790)
FINANCING ACTIVITIES
Payment of Dividends	(91,755)	(75,750)	(65,658)
Cash paid for common stock purchased	(7,407)	(35,513)	(13,723)
Excess tax benefits from share-based payments	$ 1,946	$ 4,744	3,722
Proceeds received upon exercise of stock options			6
Net cash used in financing activities	$ (97,216)	$ (106,519)	(75,653)
Effect of exchange rate changes on cash	(2,996)	(8,000)	(3,088)
Net(decrease) increase in cash and cash equivalents	26,202	(9,844)	53,134
Cash and cash equivalents at beginning of year	108,372	118,216	65,082
Cash and cash equivalents at end of year	$ 134,574	$ 108,372	$ 118,216
Supplemental disclosure of cash flow information
Cash paid for interest
Cash paid for income taxes, net	$ 82,690	$ 74,454	$ 69,354
Supplemental Disclosures of Non-Cash Items
Non-cash (increases) decreases in the minimum pension liability	14,800	(41,700)	45,700
Non-cash acquisition of assets in business combinations	$ 100	$ 24,200	$ 3,300