Schedule II: Valuation and Qualifying Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Year	$ 132,928	$ 121,473	$ 114,962
Charged to Earnings	(60,835)	15,747	13,455
Acquired Properties	3,515	0	0
Uncollectible Accounts Written-off	(7,533)	(3,237)	(5,790)
Disposed Properties	(1,585)	(1,055)	(1,154)
Balance at End of Year	66,490	132,928	121,473
Allowance for Doubtful Accounts
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Year	15,164	11,637	13,545
Charged to Earnings	10,708	7,207	3,773
Acquired Properties	3,515	0	0
Uncollectible Accounts Written-off	(7,533)	(3,237)	(5,790)
Disposed Properties	(9)	(443)	109
Balance at End of Year	21,845	15,164	11,637
Straight-line Rent Receivable Allowance
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Year	117,764	109,836	101,417
Charged to Earnings	(71,543)	8,540	9,682
Acquired Properties	0	0	0
Uncollectible Accounts Written-off	0	0	0
Disposed Properties	(1,576)	(612)	(1,263)
Balance at End of Year	$ 44,645	$ 117,764	$ 109,836