Fair Value Measurements - Additional Information (Details) (Property Funds [Member])	3 Months Ended
	Mar. 31, 2015 Investments
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Number of investments held by fund	3
Minimum [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value measurement anticipated investment holding period	1 year
Maximum [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value measurement anticipated investment holding period	10 years