CONSOLIDATED STATEMENTS OF CASH FLOWS (Parenthetical)	12 Months Ended
	Dec. 31, 2012 USD ($)	Dec. 31, 2012 GBP (£)	Dec. 31, 2011 USD ($)	Dec. 31, 2010 USD ($)
Supplemental Schedule of Noncash Investing and Financing Activities
Cash dividends declared, but not yet paid	$ 2,700,000		$ 2,700,000
Issuance of equity awards to employees in grant	2,700,000		1,500,000
Noncontrolling interest upon consolidation of joint venture			600,000
Promissory notes issued for acquisition	7,200,000		9,000,000	26,500,000
Equity issued for acquisition			27,500,000	21,100,000
Reduction in promissory note payable related to a purchase price adjustment			1,400,000
Current liability and other investments recorded related to contingent consideration	16,300,000	10,000,000
Extinguishment of receivables related to acquisition				6,400,000
Extinguishment of receivables related to funding arrangement				3,300,000
Assets acquired, net of cash	366,230,000		208,419,000	365,890,000
Liabilities assumed	$ 151,816,000		$ 54,296,000	$ 127,642,000