Commitments and Contingencies - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Loss Contingencies [Line Items]
Line of credit, performance and payment bonds	$ 199.4us-gaap_ContractualObligation	$ 192.2us-gaap_ContractualObligation
Operating Partnership [Member]
Loss Contingencies [Line Items]
Outstanding letters of credit	$ 8.5	$ 8.5

Amount of contractual obligation, including but not limited to, long-term debt, capital lease obligations, operating lease obligations, purchase obligations, and other commitments.

No definition available.

Name:	us-gaap_ContractualObligation
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant