Condensed, Consolidated Statements of Comprehensive Income (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	$ 35,642,000	$ 31,359,000	$ 107,741,000	$ 101,920,000
Other Comprehensive Income (Loss), Net of Tax [Abstract]
Foreign currency translation adjustment	2,615,000	(669,000)	2,173,000	(373,000)
Adjustment for Long-term Intercompany Transactions, Gross of Tax	432,000	(608,000)	479,000	(371,000)
Adjustment for Long-term Intercompany Transactions, Tax Benefit (Expense)	(169,000)	237,000	(187,000)	145,000
Other Comprehensive Income (Loss), Net of Tax	2,878,000	(1,040,000)	2,465,000	(599,000)
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest	38,520,000	30,319,000	110,206,000	101,321,000
Comprehensive Income (Loss), Net of Tax, Attributable to Noncontrolling Interest	1,605,000	1,190,000	4,139,000	3,300,000
Comprehensive Income (Loss), Net of Tax, Attributable to Parent	36,915,000	29,129,000	106,067,000	98,021,000
Comprehensive Income Attributable To Redeemable Noncontrolling Interests			$ 2,100,000	$ 1,500,000