Fair Value Measures and Financial Instruments - Outstanding Interest Rate Derivatives Not Designated as Cash Flow Hedges of Interest Rate Risk (Details) - Jun. 30, 2015 - Not designated as hedging instrument - Interest rate caps	USD ($) DerivativeInstrument
Derivative Instruments And Hedging Activities Disclosures [Line Items]
Interest rate caps | DerivativeInstrument	20
Interest rate caps	$ 304,812,000