Summary of Total Indebtedness (Parenthetical) (Detail) (USD $) In Millions, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Debt Instrument [Line Items]
Fair value of interest rate swap	$ 18.5	$ 20.5
Series Two Thousand Five Dash One Notes [Member]
Debt Instrument [Line Items]
Fair value of interest rate swap	8.7	10.3
Twenty Ten Senior Notes [Member]
Debt Instrument [Line Items]
Fair value of interest rate swap	3.9
Unamortized discount	2.1	2.2
Twenty Twelve Senior Notes [Member]
Debt Instrument [Line Items]
Unamortized discount	3.4	3.5
Twenty Thirteen Senior Notes [Member]
Debt Instrument [Line Items]
Unamortized discount	$ 2.6	$ 2.8

Fair value before effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 20

-Section 55

-Paragraph 7

-URI http://asc.fasb.org/extlink&oid=28370219&loc=SL20226000-175313

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 20

-Section 50

-Paragraph 3

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=20225523&loc=SL20225862-175312

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 4B

-Subparagraph (a),(c)

-URI http://asc.fasb.org/extlink&oid=7476318&loc=SL5624163-113959

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant