Debt and Credit Facilities 1.25% Convertible Debentures due 2025 (Details) - USD ($) $ / shares in Units, $ in Thousands, shares in Millions	1 Months Ended	3 Months Ended			9 Months Ended		59 Months Ended
	Dec. 31, 2015	Dec. 31, 2017	Jun. 30, 2017	Jun. 30, 2015	Jun. 30, 2018	Jun. 30, 2017	Mar. 31, 2018	Sep. 30, 2017	Mar. 13, 2017	Oct. 24, 2011
Debt Instrument [Line Items]
Document Period End Date					Jun. 30, 2018
Debt Instrument, Face Amount					$ 2,587,000			$ 2,918,100
Proceeds from Issuance of Long-term Debt					$ 0	$ 838,081
Stock Repurchased and Retired During Period, Shares					8.1	5.8	54.6
Stock Repurchased During Period, Value					$ 112,000	$ 99,100	$ 918,600
Convertible Debentures 1.25% Due 2025 [Member]
Debt Instrument [Line Items]
Convertible Debt, Noncurrent									$ 252,100
Debt Instrument, Face Amount									350,000
Proceeds from Issuance of Long-term Debt						343,600
Debt Instrument, Convertible, Carrying Amount of Equity Component									$ 97,900
Debt Instrument, Convertible, Conversion Price									$ 22.22
Convertible Debentures Two Point Seven Five Percent Due November One Twenty Thirty One [Member]
Debt Instrument [Line Items]
Convertible Debt, Noncurrent										$ 533,600
Debt Instrument, Face Amount					$ 46,600			$ 377,700		690,000
Repayments of Convertible Debt	$ 38,300	$ 331,200	$ 38,300	$ 256,200		$ 17,800
Debt Instrument, Convertible, Carrying Amount of Equity Component										$ 156,400
Debt Instrument, Convertible, Conversion Price										$ 32.30