Line of Credit Payable (Details) - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Line of Credit Facility [Line Items]
Revolving credit facility borrowing capacity	$ 900,000,000
Line of credit payable	0	$ 133,600,000
Line of Credit
Line of Credit Facility [Line Items]
Revolving credit facility borrowing capacity	900,000,000
Revolving credit facility weighted average outstanding balance	$ 18,895,000
Revolving credit facility weighted average interest rate, percent	2.60%
Option to increase facility size	$ 1,600,000,000
Line of credit payable	0
Line of credit facility available for future borrowings	$ 900,000,000
Line of Credit | LIBOR
Line of Credit Facility [Line Items]
Spread over LIBOR, percent	0.875%