| Subsequent Events (Details Textual) (USD $) Share data in Millions, except Per Share data, unless otherwise specified | 1 Months Ended | 3 Months Ended | 6 Months Ended | 6 Months Ended | 1 Months Ended | 1 Months Ended | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Jul. 31, 2012 | Jun. 30, 2012 | Mar. 31, 2012 | Jun. 30, 2011 | Jun. 30, 2012 | Jun. 30, 2011 | Jul. 30, 2012 | Jul. 27, 2012 | Jun. 30, 2012
 Maximum [Member] | Jun. 30, 2012
 Minimum [Member] | Jul. 31, 2012
 Term Loan [Member] | Jul. 26, 2012
 Term Loan [Member] | Jul. 31, 2012
 Term Loan [Member]
 Maximum [Member] | Jul. 31, 2012
 Term Loan [Member]
 Minimum [Member] | |
| Subsequent Events (Textual) [Abstract] | ||||||||||||||
| Line of credit amended facility maximum borrowing capacity | $ 500,000,000 | |||||||||||||
| Line of credit extended facility expiration date | Mar. 09, 2016 | |||||||||||||
| Percentage on interest on term loan | 2.50% | 1.50% | 2.50% | 1.50% | ||||||||||
| Margin portion of interest rate in addition to base rate | 1.50% | 0.50% | ||||||||||||
| Debt issuance costs in connection with term loan | 4,500,000 | |||||||||||||
| Remaining amount of share repurchase plan under agreement | 188,900,000 | |||||||||||||
| Subsequent Events (Additional Textual) [Abstract] | ||||||||||||||
| Repurchase of common stock share | 3.9 | 5.3 | 0.7 | |||||||||||
| Average cost per share of share repurchased | $ 46.37 | |||||||||||||
| Share repurchase program capacity authorization | 1,000,000,000 | 1,000,000,000 | 1,000,000,000 | |||||||||||
| New share repurchase program capacity authorization | $ 1,000,000,000 | |||||||||||||
| Share repurchase program expiry date | Jun. 30, 2017 | |||||||||||||
| Dividends declared per share | $ 0.30 | $ 0.30 | $ 0.20 | $ 0.60 | $ 0.33 | |||||||||
| Cash dividends, date payable | Aug. 30, 2012 | |||||||||||||