Subsequent Event (Details) (Repurchase of Equity [Member], USD $) In Millions	6 Months Ended
Jun. 30, 2011
Repurchase of Equity [Member]
Subsequent Event [Line Items]
Subsequent event, authorization date of share repurchase program	Jul. 26, 2011
Subsequent event, authorized amount under share repurchase program	$ 100

Date of subsequent event occurrence or of indication that subsequent event occurred.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 5
-Paragraph 11

Name:	us-gaap_SubsequentEventDate
Namespace Prefix:	us-gaap
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	instant