Stockholders' Equity (Details) - USD ($)		1 Months Ended		3 Months Ended		6 Months Ended
	Jan. 07, 2015	Apr. 22, 2016	Jan. 28, 2016	Apr. 30, 2016	Apr. 30, 2015	Apr. 30, 2016	Apr. 30, 2015
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common Stock, Shares, Outstanding, Beginning Balance						80,883,000
Common Stock, Value, Issued, Beginning Balance						$ 721,419,000
Issued to participants in the Employee Stock Purchase Plan (ESPP) (in shares)						11,000
Issued to participants in the Employee Stock Purchase Plan (ESPP)						$ 632,000
Issued to participants in the Dividend Reinvestment and Stock Purchase Plan (in shares)						173,000
Issued to participants in the Dividend Reinvestment and Stock Purchase Plan						$ 9,807,000
Issued to participants in the Incentive Compensation Plan (ICP) (in shares)						129,000
Issued to participants in the ICP						$ 7,425,000
Costs from issuance of common stock						$ (70,000)	$ (358,000)
Common Stock, Shares, Outstanding, Ending Balance				81,196,000		81,196,000
Common Stock, Value, Issued, Ending Balance				$ 739,213,000		$ 739,213,000
ATM Sales Agreement Aggregate Amount	$ 170,000,000
ATM Sales Agreement Commission Percentage						1.50%
Cash dividends paid per share of common stock (usd per share)				$ 0.34	$ 0.33	$ 0.67	$ 0.65
Forward Contract Indexed to Issuer's Equity [Line Items]
Forward Contract Indexed to Issuer's Equity, Shares		620,000	360,000
Forward Contract Indexed to Issuer's Equity, Forward Rate Per Share		$ 59.66	$ 57.90
Initial Forward Price Per Share		$ 58.76	$ 57.04
Forward Contract Indexed to Issuer's Equity, Settlement Alternatives						Under the terms of these FSAs, at our election, we may physically settle in shares, cash or net settle for all or a portion of our obligation under the agreements.
Forward Contract Indexed to Issuer's Equity, Classification						we have classified the FSAs as equity transactions because the FSAs are indexed to our own stock and physical settlement is within our control
Forward Contract Amount Recorded in Consolidated Financial Statements				$ 0		$ 0
Forward Contract Indexed to Issuer's Equity, Indexed Shares				980,000		980,000
Forward Contract Indexed to Issuer's Equity, Settlement Alternatives, Cash, at Fair Value				$ 56,800,000		$ 56,800,000
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income from equity method investments				(14,586,000)	$ (15,842,000)	(23,787,000)	$ (24,107,000)
Income taxes				5,835,000	5,916,000	9,212,000	9,180,000
Net income				(63,432,000)	(66,402,000)	(161,222,000)	(159,380,000)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Accumulated OCIL beginning balance, net of tax				(487,000)	(1,064,000)	(855,000)	(237,000)
Total other comprehensive income (loss)				(153,000)	94,000	215,000	(733,000)
Accumulated OCIL ending balance, net of tax				(640,000)	(970,000)	(640,000)	(970,000)
Reclassification out of Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net income				171,000	410,000	$ 677,000	527,000
Maximum
Forward Contract Indexed to Issuer's Equity [Line Items]
Forward Contract Indexed to Issuer's Equity, Settlement Date						Oct. 31, 2016
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
OCIL before reclassifications, net of tax				(324,000)	(316,000)	$ (462,000)	(1,260,000)
Amounts reclassified from accumulated OCIL, net of tax				170,000	449,000	675,000	566,000
Total other comprehensive income (loss)				(154,000)	133,000	213,000	(694,000)
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges | Reclassification out of Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income from equity method investments				277,000	735,000	1,109,000	927,000
Income taxes				(107,000)	(286,000)	(434,000)	(361,000)
Net income				170,000	449,000	675,000	566,000
Accumulated Defined Benefit Plans Adjustment
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Total other comprehensive income (loss)				1,000	(39,000)	2,000	(39,000)
Accumulated Defined Benefit Plans Adjustment | Reclassification out of Accumulated Other Comprehensive Income
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income from equity method investments				2,000	(64,000)	4,000	(64,000)
Income taxes				(1,000)	25,000	(2,000)	25,000
Net income				$ 1,000	$ (39,000)	$ 2,000	$ (39,000)