Condensed Consolidating Financial Information - Cash Flows (Details 4) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Condensed Consolidating Statements Of Cash Flows
Net cash provided by (used for) operating activities	$ 161,506	$ 307,170
Cash flows from investing activities:
Purchases of investments		1,710
Sales and maturities of investments	41	623
Capital expenditures	(129,875)	(364,234)
Proceeds from sales of assets and insurance claims	5,448	8,997
Other changes in investing	(4,439)	1,710
Investment in unconsolidated affiliates		(445)
Proceeds from merger transaction		693,450
Net cash (used for) provided by investing activities	(128,825)	340,101
Cash flows from financing activities:
Increase (decrease) in cash overdrafts	1,642	(1,017)
Proceeds from (payments for) issuance of common shares		182
Reduction in revolving credit facilities	(70,000)	(250,000)
Repurchase of common shares	(1,687)
Reduction of long-term debt	(148,045)
Dividends to shareholders	(16,922)	(17,470)
Proceeds from (payments for) commercial paper, net	1,325	(282,615)
Proceeds from revolving credit facilities	150,000
Proceeds from term Loan		300,000
Payments on term loan facility		(300,000)
Payments on term loan		(300,000)
Repurchase of common shares	(1,687)
Dividends to shareholders	16,922	17,470
Other Changes	(3,818)	(4,549)
Net cash (used for) provided by financing activities	(87,505)	(555,469)
Effect of exchange rate changes on cash and cash equivalents	968	(6,950)
Net increase (decrease) in cash and cash equivalents	(53,856)	84,852
Cash and cash equivalents, beginning of period	254,530	501,149
Cash and cash equivalents, end of period	200,674	586,001
Reportable Legal Entities | Parent Company
Condensed Consolidating Statements Of Cash Flows
Net cash provided by (used for) operating activities	1,790	10,404
Cash flows from investing activities:
Proceeds from merger transaction		5,500
Net cash (used for) provided by investing activities		5,500
Cash flows from financing activities:
Proceeds from (payments for) issuance of common shares		182
Dividends to shareholders	(19,903)	(19,797)
Proceeds from issuance of intercompany debt	22,000	14,000
Dividends to shareholders	19,903	19,797
Other Changes	(3,190)	(7,089)
Net cash (used for) provided by financing activities	(1,093)	(12,704)
Net increase (decrease) in cash and cash equivalents	697	3,200
Cash and cash equivalents, beginning of period	873	1,170
Cash and cash equivalents, end of period	1,570	4,370
Reportable Legal Entities | Guarantor Subsidiaries
Condensed Consolidating Statements Of Cash Flows
Net cash provided by (used for) operating activities	(116,240)	(101,784)
Cash flows from investing activities:
Change in intercompany balances	34,916	(11,668)
Proceeds from merger transaction		646,078
Net cash (used for) provided by investing activities	34,916	634,410
Cash flows from financing activities:
Reduction in revolving credit facilities	(70,000)	(250,000)
Proceeds from (payments for) commercial paper, net	1,325	(282,615)
Proceeds from revolving credit facilities	150,000
Proceeds from term Loan		300,000
Payments on term loan facility		(300,000)
Payments on term loan		(300,000)
Net cash (used for) provided by financing activities	81,325	(532,615)
Net increase (decrease) in cash and cash equivalents	1	11
Cash and cash equivalents, beginning of period	10	7
Cash and cash equivalents, end of period	11	18
Reportable Legal Entities | Other Subsidiaries (Non-Guarantors)
Condensed Consolidating Statements Of Cash Flows
Net cash provided by (used for) operating activities	278,937	386,877
Cash flows from investing activities:
Purchases of investments		1,710
Sales and maturities of investments	41	623
Capital expenditures	(129,875)	(364,234)
Proceeds from sales of assets and insurance claims	5,448	8,997
Change in intercompany balances	(34,916)	11,668
Other changes in investing	(4,439)
Investment in unconsolidated affiliates		(445)
Proceeds from merger transaction		41,872
Net cash (used for) provided by investing activities	(163,741)	(299,809)
Cash flows from financing activities:
Increase (decrease) in cash overdrafts	1,642	(1,017)
Repurchase of common shares	(1,687)
Reduction of long-term debt	(148,045)
Proceeds from issuance of intercompany debt	(22,000)
Repurchase of common shares	(1,687)
Other Changes	(628)	2,540
Net cash (used for) provided by financing activities	(170,718)	1,523
Effect of exchange rate changes on cash and cash equivalents	968	(6,950)
Net increase (decrease) in cash and cash equivalents	(54,554)	81,641
Cash and cash equivalents, beginning of period	253,647	499,972
Cash and cash equivalents, end of period	199,093	581,613
Consolidating Adjustments
Condensed Consolidating Statements Of Cash Flows
Net cash provided by (used for) operating activities	(2,981)	11,673
Cash flows from financing activities:
Dividends to shareholders	2,981	2,327
Proceeds from issuance of intercompany debt		(14,000)
Dividends to shareholders	(2,981)	(2,327)
Net cash (used for) provided by financing activities	$ 2,981	$ (11,673)