Debt and Financing Arrangements - Summary of Unsecured Credit Facility (Detail)	3 Months Ended
Mar. 31, 2016	Mar. 31, 2015
Debt Disclosure [Abstract]
Weighted average rates	2.50%	2.21%
Range of effective rates, minimum	1.82%	1.88%
Range of effective rates, maximum	3.50%	3.25%

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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