CONSOLIDATED STATEMENT OF COMPREHENSIVE INCOME (Parenthetical) (USD $) In Thousands, unless otherwise specified	3 Months Ended
Mar. 31, 2013	Mar. 31, 2012
Statement of Other Comprehensive Income [Abstract]
Change in net unrealized (losses) gains on available-for-sale securities, tax	$ 824	$ (12,579)

Tax effect of the appreciation (loss) in the value of unsold available-for-sale securities. Excludes amounts related to other than temporary impairment (OTTI) losses.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 220

-SubTopic 10

-Section 45

-Paragraph 10A

-Subparagraph (e)

-URI http://asc.fasb.org/extlink&oid=20435746&loc=SL7669646-108580

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 220

-SubTopic 10

-Section 45

-Paragraph 12

-URI http://asc.fasb.org/extlink&oid=20435746&loc=d3e640-108580

Name:	us-gaap_OtherComprehensiveIncomeLossAvailableForSaleSecuritiesTax
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration