Shareholders' Equity - Narrative (Details)	1 Months Ended	12 Months Ended
	Apr. 30, 2007 shares	Apr. 29, 2017 USD ($) $ / shares shares	Apr. 30, 2016 USD ($) $ / shares shares	May 02, 2015 USD ($) shares	Apr. 28, 2012 shares	Apr. 30, 2011 shares	Sep. 30, 2015 USD ($)	May 01, 2015 $ / shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock repurchase program, authorized amount | $							$ 100,000,000
Purchase of common stock (in shares)		280,168	1,997,298
Common stock repurchased and retired, value | $		$ 9,800,000	$ 62,300,000
Shares repurchased (in shares)		2,277,466
Purchase of common stock | $		$ 71,900,000
Common stock - par value per share (in dollars per share) | $ / shares		$ 0.50	$ 0.50
Dividends paid | $		$ 13,700,000	$ 13,500,000	$ 13,800,000
Compensation expense | $		12,400,000	7,400,000	4,300,000
Share price (in dollars per share) | $ / shares								$ 43.59
Unrecognized equity-based compensation cost | $		$ 26,700,000
Weighted average period for recognition of unrecognized equity-based compensation cost		2 years 11 months 28 days
2014 Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized for grant (in shares)		3,000,000
Contingent reduction in number of shares authorized for grant (in shares)		1
Number of shares available for grant (in shares)		1,187,697
Compensation expense | $		$ 12,100,000	$ 6,400,000	$ 500,000
2014 Incentive Plan | RSAs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awarded shares (in shares)		99,000	1,185,000	13,500
Award vesting period		5 years
Expected compensation expense | $		$ 25,000,000
Compensation expense | $		$ 6,600,000	$ 3,600,000	$ 500,000
Vested (in shares)		27,000	24,000	13,500
2014 Incentive Plan | RSAs | Executives and non-executive members of management
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense | $		$ 5,700,000	$ 2,800,000
2014 Incentive Plan | RSAs | Independent directors
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense | $		$ 900,000	$ 800,000	$ 1,000,000
Number of shares issued (in shares)		27,000	24,000	13,500
2014 Incentive Plan | RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awarded shares (in shares)		32,000	576,000	0
Award vesting period		5 years
Expected compensation expense | $		$ 18,600,000
Compensation expense | $		$ 5,500,000	$ 2,800,000	$ 0
Vested (in shares)		11,333	0	0
Unearned compensation expense | $		$ 10,200,000
2014 Incentive Plan | RSUs | Vesting 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting percentage		30.00%
2014 Incentive Plan | RSUs | Vesting 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting percentage		30.00%
2014 Incentive Plan | RSUs | Vesting 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting percentage		40.00%
2014 Incentive Plan | RSUs | Chief Financial Officer
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awarded shares (in shares)		32,000
2014 Incentive Plan | RSUs | Executives and non-executive members of management
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awarded shares (in shares)			576,000
2010 Stock Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized for grant (in shares)		2,000,000
Compensation expense | $		$ 200,000	$ 400,000	$ 2,800,000
2010 Stock Plan | RSAs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awarded shares (in shares)		0	0	0	100,000	640,000
Compensation expense | $		$ 0	$ 0	$ 1,500,000
Annual vesting percentage		33.30%
Vested (in shares)		33,334	33,333	633,333
Historic multiple of EBITDA, used to calculate internal enterprise value for determining size of awards					7.5	7.5
2010 Stock Plan | Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period		3 years
Compensation expense | $		$ 100,000	$ 300,000	$ 1,200,000
Awarded options to purchase number of shares (in shares)		0	0	108,000
Award term		10 years
Annual vesting percentage		33.30%
Intrinsic value of outstanding options | $		$ 500,000
2010 Stock Plan | RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awarded shares (in shares)		0	0	0		320,000
Compensation expense | $		$ 100,000	$ 100,000	$ 100,000
Award vesting percentage				100.00%
Annual vesting percentage						20.00%
Vested (in shares)		0	0	60,000
2010 Stock Plan | Bonus in Lieu of Dividends
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restriction period for awards		5 years
2010 Stock Plan | Tandem Cash Award
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense | $				$ 5,600,000
Maximum percentage of RSA award that could be the value of Tandem Cash Award				40.00%
2007 Stock Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized for grant (in shares)		1,250,000
Compensation expense | $		$ 100,000	$ 600,000	$ 1,000,000
Total number of shares with respect to which awards may granted to any participant in any calendar year		200,000
2007 Stock Plan | RSAs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awarded shares (in shares)				13,500
Compensation expense | $		$ 0	0	$ 500,000
Number of shares issued (in shares)				27,000
Vested (in shares)				13,500
Number of shares converted from RSAs to RSUs outstanding (in shares)				0
2007 Stock Plan | RSAs | Independent directors
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares issued (in shares)				13,500
2007 Stock Plan | Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation expense | $		$ 100,000	$ 600,000	$ 500,000
Awarded options to purchase number of shares (in shares)		0	0	50,500
Award term		10 years
Annual vesting percentage		33.30%
Intrinsic value of outstanding options | $		$ 700,000
2007 Stock Plan | RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares converted from RSAs to RSUs outstanding (in shares)		201,812
Number of day after termination that awards will be issued and delivered	30 days
Converted RSUs delivered (in shares)		23,188
2007 Stock Plan | Converted from RSAs to RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares converted from RSAs to RSUs outstanding (in shares)	225,000
Threshold Performance | 2014 Incentive Plan | RSAs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of RSAs that may be earned (in shares)		389,500
2020 EBITDA goal | $		$ 198,900,000
2020 EBITDA Target Performance | 2014 Incentive Plan | RSAs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of RSAs that may be earned (in shares)		779,000
2020 EBITDA goal | $		$ 221,000,000
Unearned compensation expense | $		$ 16,400,000
Maximum Performance | 2014 Incentive Plan | RSAs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of RSAs that may be earned (in shares)		1,168,500
2020 EBITDA goal | $		$ 243,100,000
Maximum Performance | 2014 Incentive Plan | RSAs | Chief Financial Officer
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awarded shares (in shares)		72,000
Maximum Performance | 2014 Incentive Plan | RSAs | Executives and non-executive members of management
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awarded shares (in shares)			1,161,000
2020 EBITDA Below Threshold Performance | 2014 Incentive Plan | RSAs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of RSAs that may be earned (in shares)		0