Segment Information - Schedule of Financial Information of Business Segments (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Segment Reporting Information [Line Items]
Investment in unconsolidated real estate ventures	$ 79,294		$ 79,294		$ 79,570
Total assets	7,037,463		7,037,463		7,091,446
Total revenues	276,003	$ 244,273	539,011	$ 473,676
Operating expenses, including depreciation and amortization	139,596	133,971	278,401	269,746
Income (loss) from operations	136,407	110,302	260,610	203,930
Gain (loss) on real estate transactions, earnout from prior acquisition and impairment of real estate	(6,019)	11,358	(6,019)	9,814
Interest expense	(37,456)	(32,802)	(73,426)	(64,161)
Non-cash interest expense related to amortization of discount on equity component of exchangeable senior notes	(1,290)	(1,240)	(2,559)	(2,473)
Interest income	826	1,625	1,928	3,339
Interest income on note receivable from Preferred Operating Partnership unit holder	659	1,212	1,872	2,425
Equity in earnings of unconsolidated real estate ventures	3,838	3,358	7,417	6,188
Equity in earnings of unconsolidated real estate ventures - gain on purchase of a joint venture partner's interest	0	0	0	26,923
Income tax (expense) benefit	(2,867)	(3,773)	(5,991)	(6,538)
Net income (loss)	94,098	90,040	183,832	179,447
Depreciation and amortization expense	46,632	43,950	96,064	86,847
Acquisition of real estate assets			(72,651)	(435,298)
Development and redevelopment of real estate assets			(12,274)	(14,400)
Rental Operations [Member]
Segment Reporting Information [Line Items]
Investment in unconsolidated real estate ventures	79,294		79,294		79,570
Total assets	6,734,180		6,734,180		6,731,292
Total revenues	240,796	211,791	472,289	411,279
Operating expenses, including depreciation and amortization	110,672	104,161	226,029	205,859
Income (loss) from operations	130,124	107,630	246,260	205,420
Interest expense	(36,214)	(31,941)	(71,035)	(62,506)
Equity in earnings of unconsolidated real estate ventures	3,838	3,358	7,417	6,188
Income tax (expense) benefit	(462)	(445)	(925)	(1,290)
Net income (loss)	97,286	78,602	181,717	147,812
Depreciation and amortization expense	43,377	41,731	92,089	82,317
Tenant Reinsurance [Member]
Segment Reporting Information [Line Items]
Total assets	33,331		33,331		44,524
Total revenues	24,313	21,654	47,168	42,209
Operating expenses, including depreciation and amortization	3,804	3,941	7,724	8,252
Income (loss) from operations	20,509	17,713	39,444	33,957
Income tax (expense) benefit	(3,866)	(3,185)	(7,129)	(5,848)
Net income (loss)	16,643	14,528	32,315	28,109
Property Management, Acquisition and Development [Member]
Segment Reporting Information [Line Items]
Total assets	269,952		269,952		$ 315,630
Total revenues	10,894	10,828	19,554	20,188
Operating expenses, including depreciation and amortization	25,120	25,869	44,648	55,635
Income (loss) from operations	(14,226)	(15,041)	(25,094)	(35,447)
Gain (loss) on real estate transactions, earnout from prior acquisition and impairment of real estate	(6,019)	11,358	(6,019)	9,814
Interest expense	(1,242)	(861)	(2,391)	(1,655)
Non-cash interest expense related to amortization of discount on equity component of exchangeable senior notes	(1,290)	(1,240)	(2,559)	(2,473)
Interest income	826	1,625	1,928	3,339
Interest income on note receivable from Preferred Operating Partnership unit holder	659	1,212	1,872	2,425
Equity in earnings of unconsolidated real estate ventures - gain on purchase of a joint venture partner's interest	0	0	0	(26,923)
Income tax (expense) benefit	1,461	(143)	2,063	600
Net income (loss)	(19,831)	(3,090)	(30,200)	3,526
Depreciation and amortization expense	3,255	2,219	3,975	4,530
Acquisition of real estate assets			(72,651)	(435,298)
Development and redevelopment of real estate assets			$ (12,274)	$ (14,400)