Condensed, Consolidated Statements of Comprehensive Income (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	$ 41,911,000	$ 35,642,000	$ 117,194,000	$ 107,741,000
Other Comprehensive Income (Loss), Net of Tax [Abstract]
Foreign currency translation adjustment	2,633,000	2,878,000	(3,708,000)	2,465,000
Other Comprehensive Income (Loss), Net of Tax	2,633,000	2,878,000	(3,708,000)	2,465,000
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest	44,544,000	38,520,000	113,486,000	110,206,000
Comprehensive Income (Loss), Net of Tax, Attributable to Noncontrolling Interest	1,264,000	1,605,000	4,400,000	4,139,000
Comprehensive Income (Loss), Net of Tax, Attributable to Parent	43,280,000	36,915,000	109,086,000	106,067,000
Comprehensive Income Attributable To Redeemable Noncontrolling Interests	$ 2,600,000	$ 2,100,000