Financial Information for the Company and Its Subsidiaries (Cash Flow Statements) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Cash flows from operating activities:
Net cash flows provided by operating activities	$ 81,773	$ 98,827
Cash flows from investing activities:
Acquisitions and related expenses	(2,990)	(126,578)
Acquisition of property and equipment	(15,691)	(14,783)
Maturities of marketable securities	2,240	0
Other	(1,509)	(220)
Net cash flows used in investing activities	(17,950)	(141,581)
Cash flows from financing activities:
Proceeds from long-term borrowings and revolving credit facility	16,197	2,227
Repayment on long-term borrowings and revolving credit facility	(40,332)	(5,213)
Distributions to owners, including noncontrolling interests	(56,801)	(47,202)
Capital contributions		0
Changes in intercompany balances with affiliates, net	0	0
Other, net	(3,664)	1,019
Net cash flows used in financing activities	(84,600)	(49,169)
Net decrease in cash and cash equivalents	(20,777)	(91,923)
Cash and cash equivalents, beginning of period	106,660	208,079
Cash and cash equivalents, end of period	85,883	116,156
Consolidation, Eliminations [Member]
Cash flows from operating activities:
Net cash flows provided by operating activities	(131,699)	(62,196)
Cash flows from investing activities:
Acquisitions and related expenses	0	62,525
Acquisition of property and equipment	0	0
Maturities of marketable securities	0
Other	0	0
Net cash flows used in investing activities	0	62,525
Cash flows from financing activities:
Proceeds from long-term borrowings and revolving credit facility	0	0
Repayment on long-term borrowings and revolving credit facility	0	0
Distributions to owners, including noncontrolling interests	131,699	62,196
Capital contributions		(62,056)
Changes in intercompany balances with affiliates, net	0	0
Other, net	0	(469)
Net cash flows used in financing activities	131,699	(329)
Net decrease in cash and cash equivalents	0	0
Cash and cash equivalents, beginning of period	0	0
Cash and cash equivalents, end of period	0	0
Parent Company [Member]
Cash flows from operating activities:
Net cash flows provided by operating activities	18,122	(33,779)
Cash flows from investing activities:
Acquisitions and related expenses	0	(62,056)
Acquisition of property and equipment	(1,509)	(2,678)
Maturities of marketable securities	0
Other	0	0
Net cash flows used in investing activities	(1,509)	(64,734)
Cash flows from financing activities:
Proceeds from long-term borrowings and revolving credit facility	15,000	0
Repayment on long-term borrowings and revolving credit facility	(37,175)	(2,175)
Distributions to owners, including noncontrolling interests	0	0
Capital contributions		0
Changes in intercompany balances with affiliates, net	(979)	(2,573)
Other, net	(4,505)	(972)
Net cash flows used in financing activities	(27,659)	(5,720)
Net decrease in cash and cash equivalents	(11,046)	(104,233)
Cash and cash equivalents, beginning of period	20,437	134,351
Cash and cash equivalents, end of period	9,391	30,118
Guarantor Subsidiaries [Member]
Cash flows from operating activities:
Net cash flows provided by operating activities	72,860	91,981
Cash flows from investing activities:
Acquisitions and related expenses	(2,990)	(127,047)
Acquisition of property and equipment	(7,320)	(2,538)
Maturities of marketable securities	0
Other	(878)	(1,322)
Net cash flows used in investing activities	(11,188)	(130,907)
Cash flows from financing activities:
Proceeds from long-term borrowings and revolving credit facility	0	0
Repayment on long-term borrowings and revolving credit facility	0	0
Distributions to owners, including noncontrolling interests	(68,547)	(10,241)
Capital contributions		62,056
Changes in intercompany balances with affiliates, net	0	0
Other, net	0	2,321
Net cash flows used in financing activities	(68,547)	54,136
Net decrease in cash and cash equivalents	(6,875)	15,210
Cash and cash equivalents, beginning of period	27,507	23,471
Cash and cash equivalents, end of period	20,632	38,681
Non-Guarantor Subsidiaries [Member]
Cash flows from operating activities:
Net cash flows provided by operating activities	122,490	102,821
Cash flows from investing activities:
Acquisitions and related expenses	0	0
Acquisition of property and equipment	(6,862)	(9,567)
Maturities of marketable securities	2,240
Other	(631)	1,102
Net cash flows used in investing activities	(5,253)	(8,465)
Cash flows from financing activities:
Proceeds from long-term borrowings and revolving credit facility	1,197	2,227
Repayment on long-term borrowings and revolving credit facility	(3,157)	(3,038)
Distributions to owners, including noncontrolling interests	(119,953)	(99,157)
Capital contributions		0
Changes in intercompany balances with affiliates, net	979	2,573
Other, net	841	139
Net cash flows used in financing activities	(120,093)	(97,256)
Net decrease in cash and cash equivalents	(2,856)	(2,900)
Cash and cash equivalents, beginning of period	58,716	50,257
Cash and cash equivalents, end of period	$ 55,860	$ 47,357