Basis of Presentation - Additional Information (Detail) $ in Millions	3 Months Ended
Mar. 31, 2016 Segment	Dec. 31, 2015 USD ($)
Debt Instrument [Line Items]
Number of reportable segment \| Segment	1
Mortgages [Member]
Debt Instrument [Line Items]
Unamortized Debt Issuance Expense		$ 4.2
Term Loans [Member]
Debt Instrument [Line Items]
Unamortized Debt Issuance Expense		$ 2.0

The remaining balance of debt issuance expenses that were capitalized and are being amortized against income over the lives of the respective bond issues. This does not include the amounts capitalized as part of the cost of the utility plant or asset.

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 210.5-02.17)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Name:	us-gaap_UnamortizedDebtIssuanceExpense
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant