Schedule III - Real Estate and Accumulated Depreciation and Amortization - Summary (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Real Estate and Accumulated Depreciation [Line Items]
Total cost basis for federal income tax purposes	$ 4,400,000
Reconciliation of real estate owned:
Balance at the beginning of year	3,789,711	$ 3,671,560	$ 3,812,294
Additions during year	291,004	478,717	210,143
Properties sold during year	(527,597)	(343,976)	(347,569)
Other reclassifications	(19,946)	(16,590)	(3,308)
Balance at end of year	3,533,172	3,789,711	3,671,560
Reconciliation of accumulated depreciation and amortization:
Balance at the beginning of year	812,207	795,486	775,617
Depreciation and amortization expense	128,384	124,618	119,156
Accumulated depreciation and amortization of properties sold, impaired and held for sale during year	(86,428)	(106,268)	(98,698)
Other reclassifications	(9,232)	(1,629)	(589)
Balance at end of year	844,931	812,207	795,486
LCIF [Member]
Real Estate and Accumulated Depreciation [Line Items]
Total cost basis for federal income tax purposes	900,000
Reconciliation of real estate owned:
Balance at the beginning of year	1,061,606	910,113	892,621
Additions during year	49,417	152,280	58,511
Properties sold during year	(379,821)	(787)	(41,016)
Other reclassifications	0	0	(3)
Balance at end of year	731,202	1,061,606	910,113
Reconciliation of accumulated depreciation and amortization:
Balance at the beginning of year	199,690	176,167	172,965
Depreciation and amortization expense	26,989	23,523	21,837
Accumulated depreciation and amortization of properties sold, impaired and held for sale during year	(44,174)	0	(18,635)
Balance at end of year	$ 182,505	$ 199,690	$ 176,167