Financial Information for the Company and Its Subsidiaries (Cash Flow Statements) (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
Cash flows from operating activities:
Net cash flows provided by operating activities	$ 351,090	$ 427,202
Cash flows from investing activities:
Acquisitions and related expenses	(351,736)	(233,490)
Acquisition of property and equipment	(64,007)	(47,006)
Increase in cash due to consolidation of previously unconsolidated affiliates	31,412	0
Purchases of marketable securities	(498)	(1,743)
Maturities of marketable securities	2,987	4,233
Other, net	(6,488)	(3,974)
Net cash flows used in investing activities	(388,330)	(281,980)
Cash flows from financing activities:
Proceeds from long-term borrowings and revolving credit facility	430,006	10,197
Repayment on long-term borrowings and revolving credit facility	(214,268)	(15,737)
Distributions to owners, including noncontrolling interests	(172,075)	(158,144)
Capital contributions	0	0
Changes in intercompany balances with affiliates, net	0	0
Other, net	(7,025)	(2,195)
Net cash flows provided by (used in) financing activities	36,638	(165,879)
Net decrease in cash and cash equivalents	(602)	(20,657)
Cash and cash equivalents, beginning of period	106,660	208,079
Cash and cash equivalents, end of period	106,058	187,422
Consolidation, Eliminations [Member]
Cash flows from operating activities:
Net cash flows provided by operating activities	(344,346)	(233,773)
Cash flows from investing activities:
Acquisitions and related expenses	301,158	31,774
Acquisition of property and equipment	0	0
Increase in cash due to consolidation of previously unconsolidated affiliates	0
Purchases of marketable securities	0	0
Maturities of marketable securities	0	0
Other, net	0	0
Net cash flows used in investing activities	301,158	31,774
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	344,346	233,773
Capital contributions	(296,689)	(29,157)
Changes in intercompany balances with affiliates, net	0	0
Other, net	(4,469)	(2,617)
Net cash flows provided by (used in) financing activities	43,188	201,999
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	79,353	(20,702)
Cash flows from investing activities:
Acquisitions and related expenses	(296,689)	(29,157)
Acquisition of property and equipment	(3,019)	(5,659)
Increase in cash due to consolidation of previously unconsolidated affiliates	0
Purchases of marketable securities	0	0
Maturities of marketable securities	0	0
Other, net	0	0
Net cash flows used in investing activities	(299,708)	(34,816)
Cash flows from financing activities:
Proceeds from long-term borrowings and revolving credit facility	423,000	0
Repayment on long-term borrowings and revolving credit facility	(204,525)	(6,525)
Distributions to owners, including noncontrolling interests	0	0
Capital contributions	0	0
Changes in intercompany balances with affiliates, net	(5,621)	524
Other, net	(9,078)	(4,102)
Net cash flows provided by (used in) financing activities	203,776	(10,103)
Net decrease in cash and cash equivalents	(16,579)	(65,621)
Cash and cash equivalents, beginning of period	20,437	134,351
Cash and cash equivalents, end of period	3,858	68,730
Guarantor Subsidiaries [Member]
Cash flows from operating activities:
Net cash flows provided by operating activities	226,593	313,286
Cash flows from investing activities:
Acquisitions and related expenses	(356,205)	(236,107)
Acquisition of property and equipment	(35,450)	(15,418)
Increase in cash due to consolidation of previously unconsolidated affiliates	0
Purchases of marketable securities	0	0
Maturities of marketable securities	0	0
Other, net	(2,217)	(779)
Net cash flows used in investing activities	(393,872)	(252,304)
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	(14)	0
Distributions to owners, including noncontrolling interests	(153,119)	(59,616)
Capital contributions	296,689	29,157
Changes in intercompany balances with affiliates, net	0	0
Other, net	3,503	2,653
Net cash flows provided by (used in) financing activities	147,059	(27,806)
Net decrease in cash and cash equivalents	(20,220)	33,176
Cash and cash equivalents, beginning of period	27,507	23,471
Cash and cash equivalents, end of period	7,287	56,647
Non-Guarantor Subsidiaries [Member]
Cash flows from operating activities:
Net cash flows provided by operating activities	389,490	368,391
Cash flows from investing activities:
Acquisitions and related expenses	0	0
Acquisition of property and equipment	(25,538)	(25,929)
Increase in cash due to consolidation of previously unconsolidated affiliates	31,412
Purchases of marketable securities	(498)	(1,743)
Maturities of marketable securities	2,987	4,233
Other, net	(4,271)	(3,195)
Net cash flows used in investing activities	4,092	(26,634)
Cash flows from financing activities:
Proceeds from long-term borrowings and revolving credit facility	7,006	10,197
Repayment on long-term borrowings and revolving credit facility	(9,729)	(9,212)
Distributions to owners, including noncontrolling interests	(363,302)	(332,301)
Capital contributions	0	0
Changes in intercompany balances with affiliates, net	5,621	(524)
Other, net	3,019	1,871
Net cash flows provided by (used in) financing activities	(357,385)	(329,969)
Net decrease in cash and cash equivalents	36,197	11,788
Cash and cash equivalents, beginning of period	58,716	50,257
Cash and cash equivalents, end of period	$ 94,913	$ 62,045