Defined Contribution Plans (Details Textual) (USD $)	1 Months Ended			12 Months Ended
	Jan. 31, 2012	Jan. 31, 2011	Mar. 31, 2007	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Oct. 31, 1989
Defined Contribution Plans (Textual) [Abstract]
Maximum pretax contribution an employee can make							100.00%
Company matching per dollar of employee contribution	$ 0.50	$ 0.35
Matching contribution percentage per participating employee	6.00%	6.00%
Employers total contribution to defined contribution plan				3,983,000	2,669,000
Employers matching contribution to defined contribution plan						0
Defined contribution plans supplemental period			5 years	5 years
Total accrued supplemental pension transition contributions				$ 3,820,000	$ 3,079,000	$ 3,148,000