CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended				6 Months Ended		12 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019	Jun. 30, 2020	Dec. 31, 2019	Jun. 30, 2019	Dec. 31, 2018
Cash flows from operating activities:
Net income (loss)	$ (240,584)	$ (80,141)	$ (110,790)	$ 14,957	$ (320,725)	$ (95,833)
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Equity in (earnings) losses of unconsolidated ventures	85,277		(12,557)		68,110	(33,867)
Depreciation and amortization	14,020		29,257		31,996	56,919
Straight-line rental income					(1,818)	(3,552)
Amortization of above/below market lease values, net					(565)	(1,737)
Amortization of premium/accretion of discount and fees on investments and borrowings, net					(6,066)	(5,701)
Amortization of deferred financing costs					6,290	4,252
Amortization of right-of-use lease assets and operating lease liabilities					49	48
Paid-in-kind interest added to loan principal, net of interest received					(6,382)	(3,738)
Distributions of cumulative earnings from unconsolidated ventures					13,429	30,879
Unrealized (gain) loss on mortgage loans and obligations held in securitization trusts, net	8,975		(5,549)		28,427	(6,578)
Realized (gain) loss on mortgage loans and obligations held in securitization trusts, net	0		0		0	(48)
Realized loss on securities from write-down to fair value					29,240	0
Realized loss on sale of real estate securities, available for sale					57,045	0
Provision for loan losses	(51)		110,258		69,881	110,258
Impairment of operating real estate	25,935		10,124		30,061	10,124
Amortization of equity-based compensation					1,891	4,556
Mortgage notes above/below market value amortization					(817)	164
Deferred income tax (benefit) expense					719	(3,589)
Other (gain) loss, net					23,531	0
Changes in assets and liabilities:
Receivables, net					2,159	(8,113)
Deferred costs and other assets					20,432	5,890
Due to related party					(1,377)	(2,672)
Other liabilities					(15,943)	5,483
Net cash provided by operating activities					29,567	63,145
Cash flows from investing activities:
Acquisition, origination and funding of loans and preferred equity held for investment, net					(66,722)	(886,397)
Repayment on loans and preferred equity held for investment					160,069	287,437
Repayment on loans held for sale					32,576	0
Proceeds from sale of real estate					161,817	0
Acquisition of and additions to real estate, related intangibles and leasing commissions					(15,196)	(9,281)
Investments in unconsolidated ventures					(47,541)	(7,801)
Proceeds from sale of investments in unconsolidated ventures					99,985	76,861
Distributions in excess of cumulative earnings from unconsolidated ventures					24,170	119,472
Repayment of real estate securities, available for sale, from sales					89,680	0
Repayment of real estate securities, available for sale, from cost recovery					2,106	0
Repayment of principal in mortgage loans held in securitization trusts					13,138	0
Net receipts on settlement of derivative instruments					19,637	1,638
Deposit on investments					0	(372)
Change in escrow deposits					(23,892)	(2,848)
Net cash provided (used in) by investing activities					449,827	(421,291)
Cash flows from financing activities:
Distributions paid on common stock					(51,705)	(111,536)
Distributions paid on common stock to noncontrolling interests					(922)	(2,682)
Shares canceled for tax withholding on vested stock awards					(1,769)	0
Borrowings from mortgage notes					13,338	85,481
Repayment of mortgage notes					(77,893)	(2,948)
Borrowings from credit facilities					255,128	1,420,569
Repayment of credit facilities					(454,188)	(977,697)
Repayment of securitization bonds					0	(57,995)
Repayment of mortgage obligations issued by securitization trusts					(13,138)	0
Payment of deferred financing costs					(6,842)	(6,972)
Contributions from noncontrolling interests					200,001	35
Distributions to noncontrolling interests					(14,169)	(1,592)
Net cash provided by (used in) financing activities					(152,159)	344,663
Effect of exchange rates on cash, cash equivalents and restricted cash					(957)	(15)
Net increase (decrease) in cash, cash equivalents and restricted cash					326,278	(13,498)
Cash, cash equivalents and restricted cash - beginning of period		195,684		187,463	195,684	187,463	$ 187,463
Cash, cash equivalents and restricted cash - end of period	521,962		173,965		521,962	173,965	195,684
Reconciliation of cash, cash equivalents, and restricted cash to consolidated balance sheets
Cash and cash equivalents								$ 437,951	$ 69,619	$ 59,838	$ 77,317
Restricted cash								84,011	126,065	114,127	110,146
Total cash, cash equivalents and restricted cash	$ 521,962	$ 195,684	$ 173,965	$ 187,463	521,962	173,965	$ 187,463	$ 521,962	$ 195,684	$ 173,965	$ 187,463
Supplemental disclosure of non-cash investing and financing activities:
Consolidation of securitization trust (VIE asset/liability additions)					0	52,346
Accrual of distribution payable					(13,164)	19,088
Foreclosure of loans held for investment, net of provision for loan losses					0	127,356
Right-of-use lease assets and operating lease liabilities					(730)	26,348
Conversion of Class B-3 common stock to Class A common stock					$ 0	$ 444