Schedule II: Valuation and Qualifying Accounts (Details) - Allowance Accounts - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Movement in Valuation Allowances and Reserves
Balance at the beginning of the year	$ 29,518	$ 36,180	$ 50,531
Additions
Amounts Charged Against Operations, net	144,135	1,177	3,174
Acquired Properties	0	0	0
Deductions
Uncollectible Accounts Written-off	(2,732)	(2,843)	(17,209)
Disposed Properties	(1,547)	(4,996)	(316)
Balance at the end of the year	$ 169,374	29,518	36,180
Discontinued Operations
Movement in Valuation Allowances and Reserves
Balance at the beginning of the year		$ 818,000
Deductions
Balance at the end of the year			$ 818,000