Debt - Senior Unsecured Credit Facility (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Feb. 26, 2020	Jul. 25, 2019	Jul. 24, 2019
Line of Credit Facility [Line Items]
Percent of unused portion, line of credit facility, triggering lower commitment fee percentage	50.00%
Senior unsecured credit facility	$ 75,000,000	$ 0
Subsequent Event
Line of Credit Facility [Line Items]
Senior unsecured credit facility				$ 75,000,000
Minimum
Line of Credit Facility [Line Items]
Commitment fee on unused percentage	0.20%
Maximum
Line of Credit Facility [Line Items]
Commitment fee on unused percentage	0.30%
Senior unsecured credit facility
Line of Credit Facility [Line Items]
Senior unsecured credit facility	$ 75,000,000	0
Interest and unused credit facility fees	$ 3,700,000	$ 1,200,000	$ 1,000,000.0
Senior unsecured credit facility | LIBOR
Line of Credit Facility [Line Items]
Basis spread on variable rate	1.40%
Senior Unsecured Credit Facility | Senior unsecured credit facility
Line of Credit Facility [Line Items]
Maximum borrowing capacity					$ 400,000,000	$ 300,000,000
Accordion feature, higher borrowing capacity						$ 600,000,000
Senior Unsecured Credit Facility | Senior unsecured credit facility | LIBOR
Line of Credit Facility [Line Items]
Basis spread on variable rate	1.45%
Senior Unsecured Credit Facility | Senior unsecured credit facility | LIBOR | Minimum
Line of Credit Facility [Line Items]
Basis spread on variable rate	1.50%
Senior Unsecured Credit Facility | Senior unsecured credit facility | LIBOR | Maximum
Line of Credit Facility [Line Items]
Basis spread on variable rate	2.25%