Commitments and Contingencies (Narrative) (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014 numberoflawsuits
Commitments and Contingencies [Abstract]
Other material lawsuits pending	0
Number of operating lease term extensions	2
Lease renewal term	5 years
Operating leases future minimum payments due	$ 42
Lease incentives	6
Loss Contingencies [Line Items]
City of Detroit UTGO Bonds	369
National [Member]
Loss Contingencies [Line Items]
City of Detroit UTGO Bonds	88
Reinstated [Member]
Loss Contingencies [Line Items]
City of Detroit UTGO Bonds	288
Reinstated [Member] | National [Member]
Loss Contingencies [Line Items]
City of Detroit UTGO Bonds	$ 70