Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 178,040	$ 219,919	$ 221,854
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	147,129	166,746	151,514
Asset impairments	614		955
Amortization of debt issuance costs and other non-cash interest	3,222	3,147	2,973
Expenses associated with debt refinancing transactions			701
Deferred income taxes	921	(3,911)	5,706
Other expenses and non-cash items	4,267	5,265	3,732
Non-cash revenue and other income	(14,528)	(8,518)	(2,639)
Income tax benefit of equity compensation		(1,479)	(525)
Non-cash equity compensation	13,286	17,903	15,394
Changes in assets and liabilities, net:
Accounts receivable, prepaid expenses and other assets	(13,913)	14,059	1,266
Accounts payable, accrued expenses and other liabilities	21,339	(39,403)	(2,210)
Income taxes payable	948	1,645	1,077
Net cash provided by operating activities	341,325	375,373	399,798
CASH FLOWS FROM INVESTING ACTIVITIES:
Expenditures for facility development and expansions	(17,576)	(41,816)	(164,880)
Expenditures for other capital improvements	(56,168)	(51,647)	(59,414)
Capitalized lease payments			(34,470)
Acquisitions, net of cash acquired	(48,867)	(43,769)	(158,366)
Decrease in restricted cash		240	1,350
Proceeds from sale of assets	970	8,412	563
(Increase) decrease in other assets	(3,605)	3,853	3,686
Payments received on direct financing lease and notes receivable	684	2,539	2,250
Net cash used in investing activities	(124,562)	(122,188)	(409,281)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from issuance of debt and borrowings from credit facility	475,500	389,000	807,000
Scheduled principal repayments	(10,000)	(5,000)
Other principal repayments of debt	(461,500)	(393,000)	(543,000)
Payment of debt issuance and other refinancing and related costs	(4,169)	(68)	(5,727)
Payment of lease obligations	(2,483)	(11,789)	(6,468)
Contingent consideration for acquisition of businesses		(5,073)
Proceeds from exercise of stock options	6,534	2,638	7,700
Purchase and retirement of common stock	(5,847)	(4,006)	(9,454)
Income tax benefit of equity compensation		1,479	525
Decrease in restricted cash for dividends		550	500
Dividends paid	(200,326)	(255,496)	(250,695)
Net cash provided by (used in) financing activities	(202,291)	(280,765)	381
NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS	14,472	(27,580)	(9,102)
CASH AND CASH EQUIVALENTS, beginning of period	37,711	65,291	74,393
CASH AND CASH EQUIVALENTS, end of period	52,183	37,711	65,291
Cash paid during the period for:
Interest (net of amounts capitalized of $0, $552, and $5,478 in 2017, 2016, and 2015, respectively)	57,485	55,966	36,992
Income taxes paid (refunded), net	$ 8,089	$ (2,137)	$ 9,966