Borrowings (Details Textual) (USD $) In Millions, unless otherwise specified	9 Months Ended
	Sep. 30, 2012	Dec. 31, 2011
Borrowings (Additional Textual) [Abstract]
Aggregate principal amount	$ 450.0
Borrowings (Textual) [Abstract]
Period of revolving credit facility	5 years
Period of term loan facility	5 years
Increase the aggregate amount of revolving credit facility	50
Percentage of pledged voting stock in domestic subsidiaries	100.00%
Percentage of pledged voting stock in foreign subsidiaries	65.00%
Percentage of Federal Funds Rate	0.50%
Percentage of Eurodollar Rate	1.00%
Percentage of original principal balance in year one	10.50%
Percentage of original principal balance in year two	12.30%
Percentage of original principal balance in year three	13.00%
Percentage of original principal balance in year four	14.80%
Percentage of original principal balance in year five	49.40%
Maturity date	Aug. 31, 2017
Credit Agreement, dividends restriction amount	50
Percentage of cumulative consolidated net income	50.00%
Percentage of net cash proceeds from equity issuances	50.00%
Actual fixed charge coverage ratio	3.36
Minimum fixed charge coverage ratio	2.25
Actual leverage ratio	2.07
Maximum leverage ratio	3.00
Minimum net worth amount	150
Outstanding letters of credit	3.9
Unused borrowing capacity under Credit Agreement	218.6
Borrowings outstanding under credit facility	222.5	193.5
Percentage of weighted average interest rate of borrowings	2.70%	3.30%
Revolving Credit Facility [Member]
Borrowings (Additional Textual) [Abstract]
Aggregate principal amount	247.5
Term Loan Facility [Member]
Borrowings (Additional Textual) [Abstract]
Aggregate principal amount	$ 202.5