Business Segments - Segment Reporting, Reconciliation of Revenues, Operating Income and Assets (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017	Dec. 31, 2016
Segment Reporting Information [Line Items]
Total revenues	$ 621,276	$ 766,183	$ 1,314,932	$ 1,395,338
Operating income	187,294	275,272	424,401	437,158
General and administrative expenses	57,615	60,077	120,043	113,694
Depreciation and amortization expenses	203,673	228,145	407,754	454,736
Earnings from unconsolidated entities, net	62,549	68,596	125,205	117,201
Interest expense	(56,314)	(75,354)	(102,575)	(148,266)
Interest and other income, net	5,641	1,892	7,617	4,677
Gains on dispositions of investments in real estate, net	94,261	83,006	289,372	180,331
Foreign currency and derivative gains (losses), net	85,382	(20,055)	44,288	(27,455)
Gains (losses) on early extinguishment of debt, net	282	(30,596)	(702)	(30,596)
Earnings before income taxes	379,095	302,761	787,606	533,050
Total assets	29,502,882		29,502,882		$ 29,481,075
Investments in and advances to unconsolidated entities	5,414,623		5,414,623		5,496,450
Assets held for sale or contribution	892,546		892,546		342,060
Notes receivable backed by real estate	0		0		34,260
Cash and cash equivalents	527,830	271,354	527,830	271,354	447,046	$ 807,316
Other assets	1,396,417		1,396,417		1,381,963
Operating Segments [Member]
Segment Reporting Information [Line Items]
Total revenues	621,276	766,183	1,314,932	1,395,338
Operating income	448,582	563,494	952,198	1,005,588
Total assets	22,462,021		22,462,021		22,960,741
Operating Segments [Member] | Real Estate Operations [Member]
Segment Reporting Information [Line Items]
Total revenues	545,579	585,529	1,106,274	1,157,639
Operating income	407,735	434,826	822,250	851,674
Total assets	22,419,962		22,419,962		22,918,099
Operating Segments [Member] | Strategic Capital [Member]
Segment Reporting Information [Line Items]
Total revenues	75,697	180,654	208,658	237,699
Operating income	40,847	128,668	129,948	153,914
Total assets	42,059		42,059		42,642
Operating Segments [Member] | U.S. [Member] | Real Estate Operations [Member]
Segment Reporting Information [Line Items]
Total revenues	491,051	529,841	990,308	1,053,988
Operating income	367,935	396,274	737,299	780,374
Total assets	18,807,476		18,807,476		19,058,610
Operating Segments [Member] | U.S. [Member] | Strategic Capital [Member]
Segment Reporting Information [Line Items]
Total revenues	17,905	130,677	33,974	142,585
Operating income	5,893	99,668	1,657	101,607
Total assets	16,438		16,438		16,818
Operating Segments [Member] | Other Americas [Member] | Real Estate Operations [Member]
Segment Reporting Information [Line Items]
Total revenues	29,948	16,444	60,379	31,533
Operating income	22,488	10,384	45,411	20,366
Total assets	1,618,701		1,618,701		1,767,385
Operating Segments [Member] | Other Americas [Member] | Strategic Capital [Member]
Segment Reporting Information [Line Items]
Total revenues	12,256	9,864	18,409	15,915
Operating income	9,032	7,587	11,939	10,732
Operating Segments [Member] | Europe [Member] | Real Estate Operations [Member]
Segment Reporting Information [Line Items]
Total revenues	12,908	22,076	30,110	40,307
Operating income	8,693	16,401	21,152	29,259
Total assets	970,749		970,749		1,008,340
Operating Segments [Member] | Europe [Member] | Strategic Capital [Member]
Segment Reporting Information [Line Items]
Total revenues	28,488	25,973	67,305	52,235
Operating income	19,382	16,342	47,045	32,732
Total assets	25,280		25,280		25,280
Operating Segments [Member] | Asia [Member] | Real Estate Operations [Member]
Segment Reporting Information [Line Items]
Total revenues	11,672	17,168	25,477	31,811
Operating income	8,619	11,767	18,388	21,675
Total assets	1,023,036		1,023,036		1,083,764
Operating Segments [Member] | Asia [Member] | Strategic Capital [Member]
Segment Reporting Information [Line Items]
Total revenues	17,048	14,140	88,970	26,964
Operating income	6,540	5,071	69,307	8,843
Total assets	341		341		544
Reconciling Items [Member]
Segment Reporting Information [Line Items]
Operating income	187,294	275,272	424,401	437,158
General and administrative expenses	57,615	60,077	120,043	113,694
Depreciation and amortization expenses	203,673	228,145	407,754	454,736
Earnings from unconsolidated entities, net	62,549	68,596	125,205	117,201
Interest expense	(56,314)	(75,354)	(102,575)	(148,266)
Interest and other income, net	5,641	1,892	7,617	4,677
Gains on dispositions of investments in real estate, net	94,261	$ 83,006	289,372	$ 180,331
Total assets	7,040,861		7,040,861		6,520,334
Investments in and advances to unconsolidated entities	5,414,623		5,414,623		5,496,450
Assets held for sale or contribution	892,546		892,546		342,060
Notes receivable backed by real estate	0		0		34,260
Cash and cash equivalents	527,830		527,830		447,046
Other assets	$ 205,862		$ 205,862		$ 200,518