Fair Value (Details) (Measured at fair value on a recurring basis, Interest Rate Hedges, USD $) In Thousands, unless otherwise specified	3 Months Ended	9 Months Ended
Jan. 27, 2013	Jan. 22, 2012	Jan. 27, 2013	Jan. 22, 2012
Measured at fair value on a recurring basis \| Interest Rate Hedges
Changes in Level 3 liabilities
Balance at the beginning of the period	$ (1,708)	$ (3,663)	$ (2,493)	$ (5,004)
Realized gains/(losses)	460	749	1,245	2,116
Unrealized gains/(losses)		(3)		(29)
Balance at the end of the period	$ (1,248)	$ (2,917)	$ (1,248)	$ (2,917)

Amount of gain (loss) recognized in other comprehensive income, arising from liabilities measured at fair value on a recurring basis using unobservable inputs (level 3).

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 820

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(1a)

-URI http://asc.fasb.org/extlink&oid=7578670&loc=d3e19207-110258

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 157

-Paragraph 32

-Subparagraph c(1)

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration