Investments in Unconsolidated Subsidiaries - Schedule of Condensed Financial Information of Equity Method Investments (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Schedule Of Equity Method Investments [Line Items]
Current assets	$ 4,385,869	$ 4,573,889
Non-current assets	15,548,581	13,871,855
Assets	19,934,450	18,445,744
Current liabilities	2,032,227	2,438,045
Non-current liabilities	4,466,814	4,571,801
Liabilities	6,499,041	7,009,846
Non-controlling interests	83,579	31,265
Revenue	1,392,590	1,426,202	$ 816,764
Operating income (loss)	1,425,824	527,871	(132,415)
Net income (loss)	1,254,345	418,751	(210,321)
Global Investment Management [Member]
Schedule Of Equity Method Investments [Line Items]
Current assets	1,304,249	1,787,277
Non-current assets	15,369,496	13,711,080
Assets	16,673,745	15,498,357
Current liabilities	526,777	1,237,589
Non-current liabilities	4,354,825	4,402,376
Liabilities	4,881,602	5,639,965
Non-controlling interests	83,579	31,265
Revenue	1,108,125	1,184,573	585,495
Operating income (loss)	972,493	209,230	(414,538)
Net income (loss)	833,189	122,560	(481,405)
Development Services [Member]
Schedule Of Equity Method Investments [Line Items]
Current assets	2,995,449	2,717,146
Non-current assets	102,508	122,457
Assets	3,097,957	2,839,603
Current liabilities	1,451,239	1,153,833
Non-current liabilities	110,649	167,757
Liabilities	1,561,888	1,321,590
Revenue	104,816	85,594	62,191
Operating income (loss)	427,407	292,141	251,557
Net income (loss)	395,697	269,841	240,034
Other [Member]
Schedule Of Equity Method Investments [Line Items]
Current assets	86,171	69,466
Non-current assets	76,577	38,318
Assets	162,748	107,784
Current liabilities	54,211	46,623
Non-current liabilities	1,340	1,668
Liabilities	55,551	48,291
Revenue	179,649	156,035	169,078
Operating income (loss)	25,924	26,500	30,566
Net income (loss)	$ 25,459	$ 26,350	$ 31,050