Fair Value Measures - Reconciliations of the changes in assets and liabilities with Level 3 inputs (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2019 USD ($) commercial_mortgage_backed_securities	Sep. 30, 2018 USD ($)
Commercial Mortgage Backed Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Number of CMBS sold | commercial_mortgage_backed_securities	2
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance		$ 40,974
Total gains and losses
Unrealized loss included in other income, net		(71)
Realized loss included in other income, net		(34)
Unrealized gain included in other income, net		0
Purchases, issuance, settlements
Return of principal received		(4,864)
Amortization included in net income, net		157
Sale of investments		(9,880)
Transfers out of Level 3 into Level 1		(12,756)
Ending balance		13,526
Cole Real Estate Investments, Inc. [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance	$ 7,844	3,264
Total gains and losses
Unrealized loss included in other income, net	(292)	0
Realized loss included in other income, net		0
Unrealized gain included in other income, net		5,102
Purchases, issuance, settlements
Return of principal received		0
Amortization included in net income, net		0
Sale of investments		(522)
Transfers out of Level 3 into Level 1		0
Ending balance	$ 7,552	$ 7,844