Consolidated Statement of Stockholders' Equity (Parenthetical) (USD $)	0 Months Ended	6 Months Ended	12 Months Ended
Apr. 24, 2012	Feb. 29, 2012	Nov. 02, 2011	Aug. 02, 2011	May 03, 2011	Jun. 30, 2012	Jun. 30, 2011	Dec. 31, 2011
Common dividends	$ 0.33	$ 0.33	$ 0.32	$ 0.32	$ 0.32	$ 0.66	$ 0.32	$ 0.96

Aggregate dividends declared during the period for each share of common stock outstanding.

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Article 3

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 505

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.3-04)

-URI http://asc.fasb.org/extlink&oid=6959260&loc=d3e187085-122770

Name:	us-gaap_CommonStockDividendsPerShareDeclared
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration