Employee Retirement Plans (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 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
Interest cost	13	11
Expected return on plan assets	(12)	(10)
Amortization of net loss	3	4
Net periodic pension cost	5	6
Non-Qualified
Net periodic pension cost for the company's defined-benefit pension plans
Interest cost	2	1
Amortization of net loss		1
Net periodic pension cost	$ 2	$ 2