Fair Value Measures - Investment in Cole REITs (Details)	12 Months Ended
	Dec. 31, 2018
CCIT II [Member] | Minimum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number of years to commence liquidity event	3 years
CCIT II [Member] | Maximum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number of years to commence liquidity event	5 years
CCPT V [Member] | Minimum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number of years to commence liquidity event	3 years
CCPT V [Member] | Maximum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number of years to commence liquidity event	6 years
CCIT III [Member] | Minimum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number of years to commence liquidity event	5 years
CCIT III [Member] | Maximum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number of years to commence liquidity event	7 years