Consolidated Statements of Income - USD ($) $ in Thousands														3 Months Ended								12 Months Ended
	Nov. 01, 2018	Sep. 05, 2018	May 30, 2018	Feb. 27, 2018	Jan. 03, 2018	Nov. 07, 2017	Sep. 01, 2017	Jun. 01, 2017	Mar. 01, 2017	Dec. 02, 2016	Sep. 01, 2016	Jun. 01, 2016	Mar. 01, 2016	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Net interest income
Interest income														$ 90,994	$ 90,386	$ 85,230	$ 78,206	$ 73,352	$ 66,833	$ 65,970	$ 57,512	$ 344,816	$ 263,667	$ 236,372
Interest expense																						194,291	146,118	120,827
Net interest income																						150,525	117,549	115,545
Provision for loan losses																						13,900	0	300
Net interest income after provision for loan losses														41,009	28,610	36,513	30,493	31,795	29,348	30,309	26,097	136,625	117,549	115,245
Other income
Operating lease income																						96,506	89,492	77,277
Tenant recoveries																						9,671	7,179	5,958
Sale of loans, net																						16,511	54,046	26,009
Realized gain (loss) on securities																						(5,808)	17,209	7,724
Unrealized gain (loss) on equity securities																						(1,605)	0	0
Unrealized gain (loss) on Agency interest-only securities																						555	1,405	(56)
Realized gain on sale of real estate, net																						95,881	11,423	20,636
Fee and other income																						26,285	18,341	21,365
Net result from derivative transactions																						15,926	(12,641)	(1,409)
Earnings (loss) from investment in unconsolidated joint ventures																						790	89	426
Gain (loss) on extinguishment/defeasance of debt																						(4,392)	(73)	5,382
Total other income																						250,320	186,470	163,312
Costs and expenses
Salaries and employee benefits																						60,117	70,463	64,270
Operating expenses																						21,696	21,421	20,552
Real estate operating expenses																						29,799	33,216	30,545
Fee expense																						5,055	4,996	3,703
Depreciation and amortization																						41,959	40,332	39,447
Total costs and expenses														36,610	40,136	38,753	43,127	52,804	39,244	40,120	38,260	158,626	170,428	158,517
Income (loss) before taxes														27,810	84,668	44,141	71,700	48,427	29,245	37,664	18,255	228,319	133,591	120,040
Income tax expense (benefit)														964	1,204	573	3,902	3,057	(576)	6,606	(1,375)	6,643	7,712	6,320
Net income (loss)														26,846	83,464	43,568	67,798	45,370	29,821	31,058	19,630	221,676	125,879	113,720
Net (income) loss attributable to noncontrolling interest in consolidated joint ventures														268	(7,843)	133	(8,422)	(92)	265	(77)	(322)	(15,864)	(226)	138
Net (income) loss attributable to noncontrolling interest in operating partnership														$ (3,011)	$ (8,991)	$ (5,294)	$ (8,501)	$ (9,172)	$ (6,499)	$ (8,868)	$ (5,838)	$ (25,797)	$ (30,377)	$ (47,131)
Earnings per share:
Basic (in dollars per share)														$ 0.24	$ 0.69	$ 0.40	$ 0.53	$ 0.41	$ 0.28	$ 0.28	$ 0.18	$ 1.85	$ 1.16	$ 1.08
Diluted (in dollars per share)														$ 0.24	$ 0.67	$ 0.40	$ 0.53	0.40	0.28	0.26	0.18	$ 1.84	$ 1.13	$ 1.06
Weighted average shares outstanding:
Basic (in shares)																						97,226,027	81,902,524	61,998,089
Diluted (in shares)																						97,652,065	109,704,880	107,638,788
Dividends per share of Class A common stock (in dollars per share)					$ 0.315													$ 0.315	$ 0.3	$ 0.3	$ 0.3	$ 1.535	$ 1.215	$ 1.285
Class A Common Stock
Costs and expenses
Net income (loss) attributable to Class A common shareholders														$ 24,103	$ 66,630	$ 38,407	$ 50,875	$ 36,106	$ 23,587	$ 22,113	$ 13,470	$ 180,015	$ 95,276	$ 66,727
Earnings per share:
Basic (in dollars per share)																						$ 1.85	$ 1.16	$ 1.08
Diluted (in dollars per share)																						$ 1.84	$ 1.13	$ 1.06
Weighted average shares outstanding:
Basic (in shares)																						97,226,027	81,902,524	61,998,089
Diluted (in shares)																						97,652,065	109,704,880	107,638,788
Dividends per share of Class A common stock (in dollars per share)	$ 0.57	$ 0.325	$ 0.325	$ 0.315		$ 0.315	$ 0.3	$ 0.3	$ 0.3	$ 0.460	$ 0.275	$ 0.275	$ 0.275	$ 0.57	$ 0.325	$ 0.325	$ 0.315					$ 1.535	$ 1.215	$ 1.285