Summary of Significant Accounting Policies Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Revenue from External Customer
Revenues	$ 435,924	$ 586,634	$ 1,303,572	$ 1,585,768
Leasing and other commissions
Revenue from External Customer
Revenues	114,947	213,242	375,465	603,094
Capital markets commissions
Revenue from External Customer
Revenues	82,956	144,666	263,838	376,213
Gains from mortgage banking activities/originations, net
Revenue from External Customer
Revenues	91,192	72,332	210,686	148,769
Management services, servicing fees and other
Revenue from External Customer
Revenues	$ 146,829	$ 156,394	$ 453,583	$ 457,692