Related Party Transactions and Investments in Non-Consolidated Entities - Investment in Sponsored REITs (Details)	12 Months Ended
	Dec. 31, 2016 entity property	Mar. 31, 2017 entity
Related Party Transactions and Investments in Non-Consolidated Entities
Number of REITs in which the entity holds non-controlling common stock interest | entity	7	7
Number of REITs in which the entity holds non-controlling preferred stock interest | entity		2
Number of properties sold | property	2
Number of entities holding mortgage loans | property	1