Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Statement of Financial Position [Abstract]
Accumulated depreciation on operating properties	$ 217,925	$ 215,856
Allowance for doubtful accounts for notes and accounts receivable	1,425	1,167
Accumulated amortization on intangible assets	85,341	53,483
Accumulated amortization on intangible liabilities	$ 21,543	$ 12,227
Preferred stock, par value (in usd per share)	$ 1	$ 1
Preferred stock, shares authorized	20,000,000	20,000,000
Preferred stock, shares issued	6,867,357	6,867,357
Preferred stock, shares outstanding	6,867,357	6,867,357
Common stock, par value (in usd per share)	$ 1	$ 1
Common stock, shares authorized	700,000,000	700,000,000
Common stock, shares issued	430,296,523	403,746,938
Treasury stock, shares	10,329,082	10,329,082