Reverse Repurchase Agreement (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Reverse Repurchase Agreement [Line Items]
Reverse repurchase agreement with non-affiliate - value	$ 860,866	$ 1,006,163
RCap [Member]
Reverse Repurchase Agreement [Line Items]
Reverse repurchase agreement with non-affiliate - value	849,400	1,000,000
Shannon [Member]
Reverse Repurchase Agreement [Line Items]
Reverse repurchase agreement with non-affiliate - value	$ 11,500

The carrying value of securities purchased to be resold in reverse repurchase transactions as of the balance sheet date.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 235

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.4-08.(m)(2)(i))

-URI http://asc.fasb.org/extlink&oid=6881521&loc=d3e23780-122690

Name:	us-gaap_SecuritiesForReverseRepurchaseAgreements
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant