Condensed Consolidating Financial Information - Cash Flows (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Condensed Consolidating Statements Of Cash Flows
Net cash provided by (used for) operating activities	$ 684,558	$ 325,773	$ 62,756
Cash flows from investing activities:
Purchases of investments	(4,323)	(676)	(6,722)
Sales and maturities of investments	18,849	4,287	13,069
Cash paid for acquisition of businesses, net of cash acquired	(2,929)	(20,859)	12,319
Capital expenditures	(427,741)	(458,938)	(574,467)
Proceeds from sales of assets and insurance claims	60,288	109,098	57,933
Net cash (used for) provided by investing activities	(355,856)	(367,088)	(497,868)
Cash flows from financing activities:
Proceeds from issuance of long-term debt		800,000	411,200
Reduction of long-term debt	(455,360)	(878,278)	(381,814)
Debt issuance costs	(1,767)	(21,277)	(11,043)
Proceeds from revolving credit facilities	1,050,000	1,135,000	725,000
Reduction in revolving credit facilities	(865,000)	(1,475,000)	(215,000)
Payments for short-term borrowings	(561)		(543)
Proceeds from (payments for) commercial paper, net		(40,000)	40,000
Proceeds from issuance of common shares, net of issuance costs		301,404	8,300
Dividends to common and preferred shareholders	(49,583)
Redeemable noncontrolling interest contribution		156,935	61,123
Noncontrolling interest contribution			20,000
Distributions to noncontrolling interest	(4,552)	(5,452)	(7,272)
Other changes	(4,750)	(8,912)	(8,399)
Cash proceeds (payments) from equity component of exchangeable debt			159,952
Purchase of capped call hedge transactions			(40,250)
Dividends to common and preferred shareholders	(49,583)	(87,098)	(68,503)
Proceeds from issuance of preferred stock, net of issuance costs		277,927
Payments on term loan			(162,500)
Proceeds from short-term borrowings		380
Repurchase of common shares			(18,071)
Net cash (used for) provided by financing activities	(331,573)	155,629	512,180
Effect of exchange rate changes on cash and cash equivalents	(6,171)	(5,263)	(29)
Net increase (decrease) in cash, cash equivalents and restricted cash	(9,042)	109,051	77,039
Cash and cash equivalents and restricted cash, beginning of period	451,080	342,029	264,990
Cash and cash equivalents and restricted cash, end of period	442,038	451,080	342,029
Consolidating Adjustments
Condensed Consolidating Statements Of Cash Flows
Net cash provided by (used for) operating activities	(64,358)	(47,497)	(132,986)
Cash flows from investing activities:
Cash paid for investments in consolidated affiliates	8,500	794,000	86,060
Net cash (used for) provided by investing activities	8,500	794,000	86,060
Cash flows from financing activities:
Dividends to common and preferred shareholders	4,752
Proceeds from parent contributions	(8,500)	(794,000)	(86,060)
Distribution from subsidiary to parent	59,606	35,012	121,070
Dividends to common and preferred shareholders		12,485	11,916
Net cash (used for) provided by financing activities	55,858	(746,503)	46,926
Parent Company | Reportable Legal Entities
Condensed Consolidating Statements Of Cash Flows
Net cash provided by (used for) operating activities	79,910	86,504	143,444
Cash flows from investing activities:
Cash paid for investments in consolidated affiliates		(587,500)	(100)
Net cash (used for) provided by investing activities		(587,500)	(100)
Cash flows from financing activities:
Proceeds from issuance of common shares, net of issuance costs	6	301,404	8,299
Dividends to common and preferred shareholders	(54,347)
Proceeds from issuance of intercompany debt	6,600	45,500
Paydown of intercompany debt	(27,700)	(21,000)	(102,000)
Other changes	(4,624)	(3,869)	(8,210)
Dividends to common and preferred shareholders		(99,583)	(80,419)
Proceeds from issuance of preferred stock, net of issuance costs		277,927
Repurchase of common shares			(18,071)
Proceeds from (payments for) issuance of intercompany debt			57,000
Net cash (used for) provided by financing activities	(80,065)	500,379	(143,401)
Net increase (decrease) in cash, cash equivalents and restricted cash	(155)	(617)	(57)
Cash and cash equivalents and restricted cash, beginning of period	474	1,091	1,148
Cash and cash equivalents and restricted cash, end of period	319	474	1,091
Guarantor Subsidiaries | Reportable Legal Entities
Condensed Consolidating Statements Of Cash Flows
Net cash provided by (used for) operating activities	(179,265)	(208,943)	(90,229)
Cash flows from investing activities:
Cash paid for acquisition of businesses, net of cash acquired		(20,859)
Change in intercompany balances	449,888	502,856	(599,974)
Net cash (used for) provided by investing activities	449,888	481,997	(599,974)
Cash flows from financing activities:
Proceeds from issuance of long-term debt		800,000	411,200
Reduction of long-term debt	(455,360)	(878,278)	(270,269)
Debt issuance costs	(1,767)	(21,277)	(11,043)
Proceeds from revolving credit facilities	1,050,000	1,135,000	725,000
Reduction in revolving credit facilities	(865,000)	(1,475,000)	(215,000)
Proceeds from (payments for) commercial paper, net		(40,000)	40,000
Paydown of intercompany debt	(7,000)		(20,000)
Proceeds from parent contributions	8,500	206,500	42,980
Cash proceeds (payments) from equity component of exchangeable debt			159,952
Purchase of capped call hedge transactions			(40,250)
Payments on term loan			(162,500)
Proceeds from (payments for) issuance of intercompany debt			20,000
Net cash (used for) provided by financing activities	(270,627)	(273,055)	680,070
Net increase (decrease) in cash, cash equivalents and restricted cash	(4)	(1)	(10,133)
Cash and cash equivalents and restricted cash, beginning of period	43	44	10,177
Cash and cash equivalents and restricted cash, end of period	39	43	44
Other Subsidiaries (Non-Guarantors) | Reportable Legal Entities
Condensed Consolidating Statements Of Cash Flows
Net cash provided by (used for) operating activities	848,271	495,709	142,527
Cash flows from investing activities:
Purchases of investments	(4,323)	(676)	(6,722)
Sales and maturities of investments	18,849	4,287	13,069
Cash paid for acquisition of businesses, net of cash acquired	(2,929)		12,319
Cash paid for investments in consolidated affiliates	(8,500)	(206,500)	(85,960)
Capital expenditures	(427,741)	(458,938)	(574,467)
Proceeds from sales of assets and insurance claims	60,288	109,098	57,933
Change in intercompany balances	(449,888)	(502,856)	599,974
Net cash (used for) provided by investing activities	(814,244)	(1,055,585)	16,146
Cash flows from financing activities:
Reduction of long-term debt			(111,545)
Payments for short-term borrowings	(561)		(543)
Proceeds from issuance of common shares, net of issuance costs	(6)		1
Dividends to common and preferred shareholders	12
Redeemable noncontrolling interest contribution		156,935	61,123
Noncontrolling interest contribution			20,000
Distributions to noncontrolling interest	(4,552)	(5,452)	(7,272)
Proceeds from issuance of intercompany debt	(6,600)	(45,500)
Paydown of intercompany debt	34,700	21,000	122,000
Proceeds from parent contributions		587,500	43,080
Distribution from subsidiary to parent	(59,606)	(35,012)	(121,070)
Other changes	(126)	(5,043)	(189)
Proceeds from short-term borrowings		380
Proceeds from (payments for) issuance of intercompany debt			(77,000)
Net cash (used for) provided by financing activities	(36,739)	674,808	(71,415)
Effect of exchange rate changes on cash and cash equivalents	(6,171)	(5,263)	(29)
Net increase (decrease) in cash, cash equivalents and restricted cash	(8,883)	109,669	87,229
Cash and cash equivalents and restricted cash, beginning of period	450,563	340,894	253,665
Cash and cash equivalents and restricted cash, end of period	$ 441,680	$ 450,563	$ 340,894