Condensed Consolidating Financial Information - Cash Flows (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Condensed Consolidating Statements Of Cash Flows
Net cash provided by (used for) operating activities	$ 430,828	$ 76,919
Cash flows from investing activities:
Purchases of investments	(5,008)	(676)
Sales and maturities of investments	14,466	2,962
Cash paid for acquisitions of businesses, net of cash acquired	(2,929)
Capital expenditures	(366,594)	(338,968)
Proceeds from sales of assets and insurance claims	26,365	86,666
Net cash (used for) provided by investing activities	(333,700)	(250,016)
Cash flows from financing activities:
Increase (decrease) in cash overdrafts	(130)	(261)
Debt issuance costs	(48)	(13,262)
Proceeds from (payments for) issuance of common shares		301,835
Reduction of long-term debt	(379,193)	(774,802)
Proceeds from (payments for) commercial paper, net		(40,000)
Proceeds from revolving credit facilities	975,000	905,000
Reduction in revolving credit facilities	(690,000)	(1,200,000)
Dividends to common and preferred shareholders	(41,643)	(61,341)
Proceeds from (payments for) short-term borrowings	497	252
Proceeds from issuance of preferred stock, net of issuance costs		278,358
Repurchase of preferred shares	79
Proceeds from issuance of long-term debt		800,000
Distributions to noncontrolling interest	(4,552)	(4,676)
Other changes	(1,611)	(3,722)
Net cash (used for) provided by financing activities	(141,759)	187,381
Effect of exchange rate changes on cash and cash equivalents	(4,421)	(5,320)
Net increase (decrease) in cash, cash equivalents and restricted cash	(49,052)	8,964
Cash and cash equivalents and restricted cash, beginning of period	451,080	342,029
Cash and cash equivalents and restricted cash, end of period	402,028	350,993
Consolidating Adjustments
Condensed Consolidating Statements Of Cash Flows
Net cash provided by (used for) operating activities	(60,924)	(40,017)
Cash flows from investing activities:
Cash paid for investments in consolidated affiliates	8,500	786,500
Net cash (used for) provided by investing activities	8,500	786,500
Cash flows from financing activities:
Dividends to common and preferred shareholders	4,224	9,317
Proceeds from parent contributions	(8,500)	(786,500)
Distribution from subsidiary to parent	56,700	30,700
Net cash (used for) provided by financing activities	52,424	(746,483)
Parent Company | Reportable Legal Entities
Condensed Consolidating Statements Of Cash Flows
Net cash provided by (used for) operating activities	69,861	82,365
Cash flows from investing activities:
Cash paid for investments in consolidated affiliates		(587,500)
Net cash (used for) provided by investing activities		(587,500)
Cash flows from financing activities:
Proceeds from (payments for) issuance of common shares	6	301,835
Proceeds from issuance of intercompany debt	4,700	20,000
Dividends to common and preferred shareholders	(45,297)	(70,658)
Proceeds from issuance of preferred stock, net of issuance costs		278,358
Repurchase of preferred shares	79
Paydown of intercompany debt	(27,700)	(21,000)
Other changes	(1,616)	(3,722)
Net cash (used for) provided by financing activities	(69,986)	504,813
Net increase (decrease) in cash, cash equivalents and restricted cash	(125)	(322)
Cash and cash equivalents and restricted cash, beginning of period	474	1,091
Cash and cash equivalents and restricted cash, end of period	349	769
Guarantor Subsidiaries | Reportable Legal Entities
Condensed Consolidating Statements Of Cash Flows
Net cash provided by (used for) operating activities	(171,500)	(203,493)
Cash flows from investing activities:
Change in intercompany balances	264,238	327,555
Net cash (used for) provided by investing activities	264,238	327,555
Cash flows from financing activities:
Debt issuance costs	(48)	(13,262)
Reduction of long-term debt	(379,193)	(774,802)
Proceeds from (payments for) commercial paper, net		(40,000)
Proceeds from revolving credit facilities	975,000	905,000
Reduction in revolving credit facilities	(690,000)	(1,200,000)
Proceeds from issuance of long-term debt		800,000
Paydown of intercompany debt	(7,194)
Proceeds from parent contributions	8,500	199,000
Net cash (used for) provided by financing activities	(92,935)	(124,064)
Net increase (decrease) in cash, cash equivalents and restricted cash	(197)	(2)
Cash and cash equivalents and restricted cash, beginning of period	42	44
Cash and cash equivalents and restricted cash, end of period	(155)	42
Other Subsidiaries (Non-Guarantors) | Reportable Legal Entities
Condensed Consolidating Statements Of Cash Flows
Net cash provided by (used for) operating activities	593,391	238,064
Cash flows from investing activities:
Purchases of investments	(5,008)	(676)
Sales and maturities of investments	14,466	2,962
Cash paid for acquisitions of businesses, net of cash acquired	(2,929)
Cash paid for investments in consolidated affiliates	(8,500)	(199,000)
Capital expenditures	(366,594)	(338,968)
Proceeds from sales of assets and insurance claims	26,365	86,666
Change in intercompany balances	(264,238)	(327,555)
Net cash (used for) provided by investing activities	(606,438)	(776,571)
Cash flows from financing activities:
Increase (decrease) in cash overdrafts	(130)	(261)
Proceeds from (payments for) issuance of common shares	(6)
Proceeds from issuance of intercompany debt	(4,700)	(20,000)
Dividends to common and preferred shareholders	(570)
Proceeds from (payments for) short-term borrowings	497	252
Paydown of intercompany debt	34,894	21,000
Distributions to noncontrolling interest	(4,552)	(4,676)
Proceeds from parent contributions		587,500
Distribution from subsidiary to parent	(56,700)	(30,700)
Other changes	5
Net cash (used for) provided by financing activities	(31,262)	553,115
Effect of exchange rate changes on cash and cash equivalents	(4,421)	(5,320)
Net increase (decrease) in cash, cash equivalents and restricted cash	(48,730)	9,288
Cash and cash equivalents and restricted cash, beginning of period	450,564	340,894
Cash and cash equivalents and restricted cash, end of period	$ 401,834	$ 350,182