Equity Investments in the Managed Programs and Real Estate - Summary of Earnings from Equity Method Investments in the Managed Programs and Real Estate (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Schedule Of Equity Method Investments
Distributions of Available Cash (Note 4)	$ 61,514	$ 64,750	$ 64,719
Income from equity method investments	61,514	64,750	64,719
Managed Programs
Schedule Of Equity Method Investments
Distributions of Available Cash (Note 4)	46,609	47,862	45,121
Income from equity method investments	3,896	5,156	7,698
Amortization of basis differences on equity method investments in the Managed Programs	(2,332)	(1,336)	(1,028)
Total equity in earnings of equity method investments in the Managed Programs	48,173	51,682	51,791
Jointly Owned Investments
Schedule Of Equity Method Investments
Income from equity method investments	15,585	15,452	16,503
Amortization of basis differences on equity method investments in the Managed Programs	(2,244)	(2,384)	(3,575)
Equity investments in real estate
Schedule Of Equity Method Investments
Income from equity method investments	$ 13,341	$ 13,068	$ 12,928