Debt and Financing Arrangements - Summary of Unsecured Credit Facility (Detail)	6 Months Ended
Jun. 30, 2015	Jun. 30, 2014
Debt Disclosure [Abstract]
Weighted average rates	2.17%	2.70%
Range of effective rates, minimum	1.88%	1.87%
Range of effective rates, maximum	3.25%	3.41%

When presenting a range of interest rates, the highest effective rate for funds borrowed under the debt agreement as of the balance sheet date.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.22(a)(1))

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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