Segment Information - Schedule of Financial Information of Business Segments (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
Segment Reporting Information [Line Items]
Investment in unconsolidated real estate ventures	$ 99,576		$ 99,576		$ 103,007
Total assets	6,458,998		6,458,998		6,071,407
Total revenues	244,273	$ 185,860	473,676	$ 359,014
Operating expenses, including depreciation and amortization	133,971	104,253	269,746	201,971
Income (loss) from operations	110,302	81,607	203,930	157,043
Gain on real estate transactions and earnout from prior acquisition	11,358	400	9,814	400
Interest expense	(32,802)	(22,811)	(64,161)	(44,242)
Non-cash interest expense related to amortization of discount on equity component of exchangeable senior notes	(1,240)	(696)	(2,473)	(1,393)
Interest income	1,625	428	3,339	1,284
Interest income on note receivable from Preferred Operating Partnership unit holder	1,212	1,212	2,425	2,425
Equity in earnings of unconsolidated real estate ventures	3,358	3,001	6,188	5,651
Equity in earnings of unconsolidated real estate ventures - gain on sale of real estate assets and purchase of partners' interests	0	0	26,923	2,857
Income tax (expense) benefit	(3,773)	(2,185)	(6,538)	(4,433)
Net income (loss)	90,040	60,956	179,447	119,592
Depreciation and amortization expense	43,950	31,552	86,847	61,980
Acquisition of real estate assets			(435,298)	(240,892)
Development and redevelopment of real estate assets			(14,400)	(9,926)
Rental Operations [Member]
Segment Reporting Information [Line Items]
Investment in unconsolidated real estate ventures	99,576		99,576		103,007
Total assets	6,130,870		6,130,870		5,674,030
Total revenues	211,791	161,024	411,279	309,918
Operating expenses, including depreciation and amortization	104,161	77,326	205,859	152,835
Income (loss) from operations	107,630	83,698	205,420	157,083
Interest expense	(31,941)	(22,703)	(62,506)	(43,860)
Equity in earnings of unconsolidated real estate ventures	3,358	3,001	6,188	5,651
Income tax (expense) benefit	(445)	(325)	(1,290)	(1,079)
Net income (loss)	78,602	63,671	147,812	117,795
Depreciation and amortization expense	41,731	29,117	82,317	57,382
Tenant Reinsurance [Member]
Segment Reporting Information [Line Items]
Total assets	38,749		38,749		37,696
Total revenues	21,654	17,340	42,209	33,850
Operating expenses, including depreciation and amortization	3,941	3,283	8,252	6,211
Income (loss) from operations	17,713	14,057	33,957	27,639
Interest income	3	4	6	8
Income tax (expense) benefit	(3,185)	(2,429)	(5,848)	(4,303)
Net income (loss)	14,531	11,632	28,115	23,344
Property Management, Acquisition and Development [Member]
Segment Reporting Information [Line Items]
Total assets	289,379		289,379		$ 359,681
Total revenues	10,828	7,496	20,188	15,246
Operating expenses, including depreciation and amortization	25,869	23,644	55,635	42,925
Income (loss) from operations	(15,041)	(16,148)	(35,447)	(27,679)
Gain on real estate transactions and earnout from prior acquisition	11,358	400	9,814	400
Interest expense	(861)	(108)	(1,655)	(382)
Non-cash interest expense related to amortization of discount on equity component of exchangeable senior notes	(1,240)	(696)	(2,473)	(1,393)
Interest income	1,622	424	3,333	1,276
Interest income on note receivable from Preferred Operating Partnership unit holder	1,212	1,212	2,425	2,425
Equity in earnings of unconsolidated real estate ventures - gain on sale of real estate assets and purchase of partners' interests	0	0	26,923	2,857
Income tax (expense) benefit	(143)	569	600	949
Net income (loss)	(3,093)	(14,347)	3,520	(21,547)
Depreciation and amortization expense	2,219	2,435	4,530	4,598
Acquisition of real estate assets			(435,298)	(240,892)
Development and redevelopment of real estate assets			$ (14,400)	$ (9,926)