Fair Value of Financial Instruments Assets and Liabilities Measured at Fair Value on a Recurring Basis (Footnote Information) (Detail) (Fair Value, Measurements, Recurring, USD $) In Thousands, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets	$ 15,008,982	[1]	$ 13,331,120	[2]
Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets	7,414,814	[1]	5,857	[2]
Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets	1,316,784	[1]	1,314,951	[2]
Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets	6,277,384	[1]	12,010,312	[2]
Noncontrolling Interests | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets	100,000		2,000
Noncontrolling Interests | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets	$ 1,100,000		$ 1,100,000

[1] Included in Level 1 and Level 3 assets are $100 million and $1.1 billion, respectively, attributable to noncontrolling interests calculated based on the ownership percentages of the noncontrolling interests.

[2] Included in Level 1 and Level 3 assets are $2 million and $1.1 billion, respectively, attributable to noncontrolling interests calculated based on the ownership percentages of the noncontrolling interests.