Income Taxes (Details Textual) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Income Taxes (Textual) [Abstract]
Income taxes paid	$ 36,300,000	$ 48,900,000	$ 24,800,000
Deferred tax assets	654,000	1,299,000
Deferred tax asset related to U.S. foreign tax credit	2,900,000
Valuation allowance amount	0	0
Tax credit carryforwards		2,000,000
Amount from exercise of awards	0
Tax benefit realized from the exercise of awards	400,000	0
Interest and penalties accrued	100,000	200,000
Interest and penalties expense	100,000	100,000
State
Income Taxes (Textual) [Abstract]
Operating loss carryforwards with expiration date	13,200,000
Deferred tax assets	600,000
Operating loss carryforwards valuation allowance	0
Operating loss carryforwards	600,000
Canadian
Income Taxes (Textual) [Abstract]
Deferred tax assets	100,000
Operating loss carryforwards valuation allowance	0
Operating loss carryforwards	400,000
Deferred tax asset with respect to Canadian net operating loss carryforwards	$ 700,000