Segment Reporting - Segment Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Assets
Long-lived assets	$ 5,810,599	$ 6,102,017
Total assets	8,453,954	8,742,089
Real Estate Ownership
Assets
Long-lived assets	5,787,071	6,079,803
Total assets	8,242,263	8,537,544
Real Estate Ownership | UNITED STATES
Assets
Long-lived assets	3,784,905	3,794,232
Total assets	5,517,050	5,435,251
Real Estate Ownership | Germany
Assets
Long-lived assets	545,672	581,283
Total assets	718,397	790,895
Real Estate Ownership | Other International
Assets
Long-lived assets	1,456,494	1,704,288
Total assets	2,006,816	2,311,398
Investment Management
Assets
Long-lived assets	23,528	22,214
Total assets	$ 211,691	$ 204,545