Schedule of Debt and Equity Offering Costs (Detail) $ in Millions	Dec. 31, 2014 USD ($)
Deferred Offering Costs [Line Items]
Debt and equity offering costs	$ 14.5
Debt Costs Associated With Acquisitions
Deferred Offering Costs [Line Items]
Debt and equity offering costs	3.7
Backstops Commitments Associated With Acquisitions
Deferred Offering Costs [Line Items]
Debt and equity offering costs	10.5
Rights and Other Equity Offering Costs
Deferred Offering Costs [Line Items]
Debt and equity offering costs	$ 0.3