Condensed Consolidating Financial Information - Cash Flows (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Condensed Consolidating Statements Of Cash Flows
Net cash provided by (used for) operating activities	$ (57,991)	$ 161,506
Cash flows from investing activities:
Purchases of investments	(4)
Sales and maturities of investments	91	41
Capital expenditures	(183,427)	(129,875)
Proceeds from sales of assets and insurance claims	3,253	5,448
Other changes in investing	(106)	(4,439)
Net cash (used for) provided by investing activities	(180,193)	(128,825)
Cash flows from financing activities:
Increase (decrease) in cash overdrafts	(469)	1,642
Proceeds from issuance of long-term debt	411,200
Debt issuance costs	(10,439)
Proceeds from (payments for) issuance of common shares	8,300
Reduction of long-term debt	(170,491)	(148,045)
Dividends to shareholders	(17,040)	(16,922)
Proceeds from (payments for) short-term borrowings	16	(628)
Purchase of capped call hedge transactions	(40,250)
Cash proceeds from equity component of exchangeable debt	159,952
Other Changes	(5,341)	(3,190)
Proceeds from revolving credit facilities		150,000
Reduction in revolving credit facilities		(70,000)
Repurchase of common shares		(1,687)
Proceeds from (payments for) commercial paper, net		1,325
Payments on term loan	(162,500)
Net cash (used for) provided by financing activities	172,938	(87,505)
Effect of exchange rate changes on cash and cash equivalents	1,841	968
Net increase (decrease) in cash and cash equivalents	(63,405)	(53,856)
Cash and cash equivalents, beginning of period	264,093	254,530
Cash and cash equivalents, end of period	200,688	200,674
Reportable Legal Entities | Parent Company
Condensed Consolidating Statements Of Cash Flows
Net cash provided by (used for) operating activities	70,492	1,790
Cash flows from financing activities:
Proceeds from (payments for) issuance of common shares	8,300
Dividends to shareholders	(20,020)	(19,903)
Proceeds from issuance of intercompany debt	20,000	22,000
Paydown of intercompany debt	(66,000)
Other Changes	(5,341)	(3,190)
Net cash (used for) provided by financing activities	(63,061)	(1,093)
Net increase (decrease) in cash and cash equivalents	7,431	697
Cash and cash equivalents, beginning of period	1,148	873
Cash and cash equivalents, end of period	8,579	1,570
Reportable Legal Entities | Guarantor Subsidiaries
Condensed Consolidating Statements Of Cash Flows
Net cash provided by (used for) operating activities	(112,431)	(116,240)
Cash flows from investing activities:
Change in intercompany balances	(198,035)	34,916
Net cash (used for) provided by investing activities	(198,035)	34,916
Cash flows from financing activities:
Proceeds from issuance of long-term debt	411,200
Debt issuance costs	(10,439)
Reduction of long-term debt	(57,670)
Purchase of capped call hedge transactions	(40,250)
Cash proceeds from equity component of exchangeable debt	159,952
Proceeds from issuance of intercompany debt	20,000
Paydown of intercompany debt	(20,000)
Proceeds from revolving credit facilities		150,000
Reduction in revolving credit facilities		(70,000)
Proceeds from (payments for) commercial paper, net		1,325
Payments on term loan	(162,500)
Net cash (used for) provided by financing activities	300,293	81,325
Net increase (decrease) in cash and cash equivalents	(10,173)	1
Cash and cash equivalents, beginning of period	10,177	10
Cash and cash equivalents, end of period	4	11
Reportable Legal Entities | Other Subsidiaries (Non-Guarantors)
Condensed Consolidating Statements Of Cash Flows
Net cash provided by (used for) operating activities	53,928	278,937
Cash flows from investing activities:
Purchases of investments	(4)
Sales and maturities of investments	91	41
Capital expenditures	(183,427)	(129,875)
Proceeds from sales of assets and insurance claims	3,253	5,448
Change in intercompany balances	198,035	(34,916)
Other changes in investing	(106)	(4,439)
Net cash (used for) provided by investing activities	17,842	(163,741)
Cash flows from financing activities:
Increase (decrease) in cash overdrafts	(469)	1,642
Reduction of long-term debt	(112,821)	(148,045)
Proceeds from (payments for) short-term borrowings	16	(628)
Proceeds from issuance of intercompany debt	(40,000)	(22,000)
Paydown of intercompany debt	86,000
Payments on parent (Equity or N/P)	(67,000)
Repurchase of common shares		(1,687)
Net cash (used for) provided by financing activities	(134,274)	(170,718)
Effect of exchange rate changes on cash and cash equivalents	1,841	968
Net increase (decrease) in cash and cash equivalents	(60,663)	(54,554)
Cash and cash equivalents, beginning of period	252,768	253,647
Cash and cash equivalents, end of period	192,105	199,093
Consolidating Adjustments
Condensed Consolidating Statements Of Cash Flows
Net cash provided by (used for) operating activities	(69,980)	(2,981)
Cash flows from financing activities:
Dividends to shareholders	2,980	2,981
Payments on parent (Equity or N/P)	67,000
Net cash (used for) provided by financing activities	$ 69,980	$ 2,981