Investments - Schedule of Activity in Real Estate Assets Held for Sale (Details)
$ in Thousands
3 Months Ended
Mar. 31, 2017
USD ($)
Property
Number of Properties  
Balance, December 31, 2016 | Property 44
Transfers from real estate investments held and used | Property 27
Sales | Property (12)
Transfers to real estate investments held and used | Property (6)
Balance, March 31, 2017 | Property 53
Carrying Value  
Balance, December 31, 2016 $ 160,570
Transfers from real estate investments held and used 59,015
Sales (34,619)
Transfers to real estate investments held and used (42,644)
Impairments (11,616)
Balance, March 31, 2017 $ 130,706