Fair Value of Financial Instruments Assets and Liabilities Measured at Fair Value on a Recurring Basis (Parenthetical) (Detail) (Fair Value, Measurements, Recurring, USD $) In Thousands, unless otherwise specified	Dec. 31, 2013		Dec. 31, 2012
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets	$ 13,331,120	[1]	$ 12,244,783	[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	5,857	[1]	5,664	[2]
Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets	1,314,951	[1]	859,141	[2]
Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets	12,010,312	[1]	11,379,978	[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	2,000		1,100
Noncontrolling Interests | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets	1,000,000		708,000
Noncontrolling Interests | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total assets			$ 8,700

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

[2] Included in Level 1, Level 2, and Level 3 assets are $1 million, $9 million and $708 million, respectively, attributable to noncontrolling interests calculated based on the ownership percentages of the noncontrolling interests.