Quarterly Results of Operations (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended										12 Months Ended
	Dec. 31, 2017		Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016		Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Summary of Unaudited Quarterly Results of Operations
Revenues as reported and adjusted	$ 1,104,257	[1]	$ 1,091,483	$ 1,058,602	$ 1,062,298	$ 1,078,321	$ 1,079,133	[2]	$ 1,076,657	$ 1,047,050	$ 4,316,641	$ 4,281,160	$ 3,859,826
Net income (loss) attributable to common stockholders	$ (111,523)	[1]	$ 74,043	$ 188,429	$ 312,639	$ 333,044	$ 334,910	[2]	$ 195,474	$ 148,969	$ 463,595	$ 1,012,397	$ 818,344
Net income (loss) attributable to common stockholders per share:
Basic	$ (0.31)	[1]	$ 0.2	$ 0.51	$ 0.86	$ 0.92	$ 0.93	[2]	$ 0.55	$ 0.42	$ 1.26	$ 2.83	$ 2.35
Diluted	$ (0.31)	[1]	$ 0.2	$ 0.51	$ 0.86	$ 0.91	$ 0.93	[2]	$ 0.54	$ 0.42	$ 1.26	$ 2.81	$ 2.34
Quarterly Results of Operations (Textuals) [Abstract]
Decreases in net income amounts and per share attributable to gains on sales of real estate							$ 162,351		$ 1,530
Impairment of assets	$ 99,821										$ 124,483	$ 37,207	$ 2,220
Provision for loan losses	$ 62,966										$ 62,966	$ 10,215	$ 0

[1] The decrease in net income (loss) and amounts per share are primarily attributable to $99,821,100 impairment of assets and $62,966,000 provision for loan losses recognized in the fourth quarter as compared to none in the third quarter.

[2] The increase in net income and amounts per share are primarily attributable to gains on sales of real estate of $162,351,000 for the third quarter as compared to gains of $1,530,000 for the second quarter.