Employee Benefit Plans (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Defined Contribution Pension and Other Postretirement Plans Disclosure [Abstract]
Expected future benefit payments in years one through five for post-retirement medical plan	$ 5,000,000
Defined Benefit Plan, Expected Future Benefit Payments in Five Fiscal Years Thereafter	7,000,000
Maximum age for retire employees to be covered under post-retirement medical plan	65
Defined Benefit Plan, Benefit Obligation	16,000,000
Defined Benefit Plan, Net Periodic Benefit Cost	2,000,000	2,000,000	2,000,000
Other Labor-related Expenses	45,000,000	40,000,000	41,000,000
Employer matching contribution for each $1 of employee deferral	1.00
Employee contribution to be matched by the Company	0.08
Defined Contribution Plan, Employer Discretionary Contribution Amount	$ 10,000,000	$ 10,000,000	$ 10,000,000