Variable Interest Entities and Asset Securitizations - Additional Information (Detail) (USD $)	Mar. 31, 2014	Dec. 31, 2013
Variable Interest Entity Disclosure [Abstract]
Carrying value of loans in the Securitization trusts	$ 117,000,000	$ 121,000,000
Combined outstanding principal amount of mortgage-backed securities issued by qualified special purpose trust held by unrelated parties	18,000,000	18,000,000
Other assets for its "investment" in the common securities recognized by the company of various trusts	34,000,000	34,000,000
Total assets of real estate partnerships in which the company invested	1,300,000,000	1,300,000,000
Maximum exposure to loss of investments in real estate partnerships	250,000,000	236,000,000
Unfunded commitments included in company's maximum exposure to loss of investments in real estate partnerships	$ 57,000,000	$ 45,000,000