Income Taxes - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Operating Loss Carryforwards [Line Items]
Income taxes paid	$ 80,622,000	$ 75,403,000	$ 69,828,000
Range of expiration dates for portions of net operating loss carryforwards	2013 through 2032
Accrued interest and penalties related to uncertain tax positions	79,000	188,000
Total amount of unrecognized tax benefits that would affect effective tax rate	294,000	806,000
Federal Income Tax
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	22,687,000
Federal Income Tax | Beginning of Range
Operating Loss Carryforwards [Line Items]
Fiscal years open for audit	2009
Federal Income Tax | End of Range
Operating Loss Carryforwards [Line Items]
Fiscal years open for audit	2012
State Income Tax
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	$ 84,311,000
State Income Tax | Beginning of Range
Operating Loss Carryforwards [Line Items]
Fiscal years open for audit	2008
State Income Tax | End of Range
Operating Loss Carryforwards [Line Items]
Fiscal years open for audit	2012
United Kingdom | Beginning of Range
Operating Loss Carryforwards [Line Items]
Fiscal years open for audit	2008
United Kingdom | End of Range
Operating Loss Carryforwards [Line Items]
Fiscal years open for audit	2012