Employee Retirement Plans (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Net periodic pension cost for the company's defined-benefit pension plans
Number of regional multi-employer pension plans in which the entity participates			21
Qualified
Net periodic pension cost for the company's defined-benefit pension plans
Service cost	$ 1	$ 1	$ 3	$ 3
Interest cost	12	10	38	32
Expected return on plan assets	(11)	(10)	(35)	(30)
Amortization of net loss	2	4	8	12
Net periodic pension cost	4	5	14	17
Non-Qualified
Net periodic pension cost for the company's defined-benefit pension plans
Interest cost	2	2	6	5
Amortization of net loss	1	1	1	2
Net periodic pension cost	$ 3	$ 3	$ 7	$ 7