Income Taxes (Details Textual) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Operating Loss Carryforwards [Line Items]
Deferred tax assets	$ 1,299,000	$ 1,207,000
Income Taxes (Textual) [Abstract]
Income taxes paid	48,900,000	24,800,000
Income tax refunds			24,200,000
Deferred tax asset related to U.S. foreign tax credit	2,000,000
Foreign tax credit valuation allowance, Amount	0	0
Tax credit carryforwards		800,000
Amount from exercise of awards	0	200,000
Valuation allowance amount	0	0
Tax benefits realized from exercise of awards	307,000	876,000	566,000
Interest and penalties expense	100,000	100,000
Interest and penalties accrued	200,000	300,000
State [Member]
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards with expiration date	13,900,000
Deferred tax asset with respect to net operating loss carryforwards	600,000
Operating loss carryforwards		600,000
Operating loss carryforwards valuation allowance	0	0
Canadian [Member]
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	2,900,000
Deferred tax assets	700,000
Deferred tax asset with respect to Canadian net operating loss carryforwards		600,000
Operating loss carryforwards valuation allowance	$ 0	$ 0