Subsequent Events (Details) (Preferred stock, USD $) In Millions, except Per Share data, unless otherwise specified	1 Months Ended
Feb. 29, 2012	May 31, 2012 Preferred dividend	May 02, 2012 Preferred dividend
Subsequent Events
Cash dividend declared (in dollars per share)	$ 1.375	$ 1.375
Aggregate dividend payable			$ 2.8

The aggregate amount of dividends declared, but not paid, as of the financial reporting date.

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 95

-Paragraph 32

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 50

-Paragraph 3

-URI http://asc.fasb.org/extlink&oid=6367179&loc=d3e4304-108586

Name:	us-gaap_DividendsPayableAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant