Employee Benefit Plans (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2010
Employee Benefit Plans (Textual) [Abstract]
Defined benefit plan funded percentage	50.00%
Percentage of annual compensation per employee	6.00%
Defined benefit plan contributions by employer	$ 3,000,000
Defined contribution plan employers matching contribution annual vesting percentage after three years	100.00%
Defined contribution plan employers matching contribution annual vesting percentage	20.00%
Defined contribution plan employers matching contribution annual vesting period	2 years
Period of defined contribution plan employers matching contribution annual vesting 100 percentage	3 years
Pension contributions	$ 1,100,000	$ 1,000,000
General discussion of pension and other postretirement benefits	We maintain a defined contribution retirement plan in accordance with Section 401(k) of the Internal Revenue Code, which allows eligible participating employees to defer receipt of up to 50% of their annual compensation and contribute such amount to one or more investment funds.