Employee Retirement Plans (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 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	$ 2	$ 2
Interest cost	13	11	26	22
Expected return on plan assets	(12)	(10)	(24)	(20)
Amortization of net loss	3	4	6	8
Net periodic pension cost	5	6	10	12
Non-Qualified
Net periodic pension cost for the company's defined-benefit pension plans
Interest cost	2	2	4	3
Amortization of net loss				1
Net periodic pension cost	$ 2	$ 2	$ 4	$ 4