Fair Value Measurements - Additional Information (Details) - Property Funds [Member]	12 Months Ended
	Dec. 31, 2015 Investments
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Number of investments held by fund	4
Minimum
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value measurement anticipated investment holding period	1 year
Maximum
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value measurement anticipated investment holding period	10 years