Notes Payable (New Credit Facility) (Details) - Credit Facility		12 Months Ended
	Jan. 03, 2018 USD ($)	Dec. 31, 2017 USD ($)
Line of Credit Facility [Line Items]
Maximum borrowing capacity		$ 500,000,000
Investment entity cap		$ 90,000,000
Minimum
Line of Credit Facility [Line Items]
Unencumbered interest coverage ratio		2.0
LIBOR
Line of Credit Facility [Line Items]
Basis spread on variable rate (percent)		1.10%
LIBOR | Minimum
Line of Credit Facility [Line Items]
Basis spread on variable rate (percent)		1.10%
LIBOR | Maximum
Line of Credit Facility [Line Items]
Basis spread on variable rate (percent)		1.45%
Federal Funds Rate
Line of Credit Facility [Line Items]
Basis spread on variable rate (percent)		0.50%
One-month LIBOR
Line of Credit Facility [Line Items]
Basis spread on variable rate (percent)		1.00%
New Credit Facility | Subsequent Event
Line of Credit Facility [Line Items]
Maximum borrowing capacity	$ 1,000,000,000
Additional borrowing capacity	500,000,000
Total borrowing availability	$ 1,500,000,000.0
New Credit Facility | Subsequent Event | Minimum
Line of Credit Facility [Line Items]
Unencumbered interest coverage ratio	1.75
New Credit Facility | Subsequent Event | Maximum
Line of Credit Facility [Line Items]
Secured leverage ratio (percent)	40.00%
New Credit Facility | Subsequent Event | LIBOR
Line of Credit Facility [Line Items]
Basis spread on variable rate (percent)	1.05%
New Credit Facility | Subsequent Event | Federal Funds Rate
Line of Credit Facility [Line Items]
Basis spread on variable rate (percent)	0.50%
New Credit Facility | Subsequent Event | One-month LIBOR
Line of Credit Facility [Line Items]
Basis spread on variable rate (percent)	1.00%