Plan Assets Measured at Fair Value on a Recurring Basis (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013		Dec. 31, 2012
Schedule Of Pension And Other Postretirment Plan Assets By Fair Value [Line Items]
Securities	$ (200)	[1]	$ (185)	[1]
Equity Securities [Member]
Schedule Of Pension And Other Postretirment Plan Assets By Fair Value [Line Items]
Securities	(48)	[1]	(106)	[1]
Equity Securities [Member] | Growth Equity Securities [Member]
Schedule Of Pension And Other Postretirment Plan Assets By Fair Value [Line Items]
Securities			(50)	[1],[2]
Equity Securities [Member] | Value Equity Securities [Member]
Schedule Of Pension And Other Postretirment Plan Assets By Fair Value [Line Items]
Securities	(8)	[1]	(52)	[1]
Equity Securities [Member] | Blended Equity Securities [Member]
Schedule Of Pension And Other Postretirment Plan Assets By Fair Value [Line Items]
Securities	(40)	[1],[2]	(4)	[1]
Mutual And Exchange Traded Funds [Member]
Schedule Of Pension And Other Postretirment Plan Assets By Fair Value [Line Items]
Securities	(134)	[1]	(42)	[1]
Mutual And Exchange Traded Funds [Member] | Money Market Funds
Schedule Of Pension And Other Postretirment Plan Assets By Fair Value [Line Items]
Securities	(7)	[1]	(4)	[1]
Mutual And Exchange Traded Funds [Member] | International Fund [Member]
Schedule Of Pension And Other Postretirment Plan Assets By Fair Value [Line Items]
Securities	(43)	[1]	(29)	[1]
Mutual And Exchange Traded Funds [Member] | Domestic Fund [Member]
Schedule Of Pension And Other Postretirment Plan Assets By Fair Value [Line Items]
Securities	(41)	[1]
Mutual And Exchange Traded Funds [Member] | Debt Fund [Member]
Schedule Of Pension And Other Postretirment Plan Assets By Fair Value [Line Items]
Securities	(20)	[1]
Mutual And Exchange Traded Funds [Member] | Alternative Strategies Fund [Member]
Schedule Of Pension And Other Postretirment Plan Assets By Fair Value [Line Items]
Securities	(17)	[1]
Mutual And Exchange Traded Funds [Member] | Commodities Investment [Member]
Schedule Of Pension And Other Postretirment Plan Assets By Fair Value [Line Items]
Securities	(6)	[1]	(9)	[1]
Debt Securities [Member]
Schedule Of Pension And Other Postretirment Plan Assets By Fair Value [Line Items]
Securities	(18)	[1]	(37)	[1]
Debt Securities [Member] | US Treasury Securities [Member]
Schedule Of Pension And Other Postretirment Plan Assets By Fair Value [Line Items]
Securities	(3)	[1]	(13)	[1]
Debt Securities [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises
Schedule Of Pension And Other Postretirment Plan Assets By Fair Value [Line Items]
Securities	(13)	[1]	(21)	[1]
Debt Securities [Member] | Non Agency Residential Mortgage Backed Securities [Member]
Schedule Of Pension And Other Postretirment Plan Assets By Fair Value [Line Items]
Securities	(2)	[1]	(2)	[1]
Debt Securities [Member] | Corporate Bond Securities [Member]
Schedule Of Pension And Other Postretirment Plan Assets By Fair Value [Line Items]
Securities			(1)	[1],[3]
Fair Value, Inputs, Level 1
Schedule Of Pension And Other Postretirment Plan Assets By Fair Value [Line Items]
Securities	(64)	[1]	(161)	[1]
Fair Value, Inputs, Level 1 | Equity Securities [Member]
Schedule Of Pension And Other Postretirment Plan Assets By Fair Value [Line Items]
Securities	(48)	[1]	(106)	[1]
Fair Value, Inputs, Level 1 | Equity Securities [Member] | Growth Equity Securities [Member]
Schedule Of Pension And Other Postretirment Plan Assets By Fair Value [Line Items]
Securities			(50)	[1],[2]
Fair Value, Inputs, Level 1 | Equity Securities [Member] | Value Equity Securities [Member]
Schedule Of Pension And Other Postretirment Plan Assets By Fair Value [Line Items]
Securities	(8)	[1]	(52)	[1]
Fair Value, Inputs, Level 1 | Equity Securities [Member] | Blended Equity Securities [Member]
Schedule Of Pension And Other Postretirment Plan Assets By Fair Value [Line Items]
Securities	(40)	[1],[2]	(4)	[1]
Fair Value, Inputs, Level 1 | Mutual And Exchange Traded Funds [Member]
Schedule Of Pension And Other Postretirment Plan Assets By Fair Value [Line Items]
Securities	(13)	[1]	(42)	[1]
Fair Value, Inputs, Level 1 | Mutual And Exchange Traded Funds [Member] | Money Market Funds
Schedule Of Pension And Other Postretirment Plan Assets By Fair Value [Line Items]
Securities	(7)	[1]	(4)	[1]
Fair Value, Inputs, Level 1 | Mutual And Exchange Traded Funds [Member] | International Fund [Member]
Schedule Of Pension And Other Postretirment Plan Assets By Fair Value [Line Items]
Securities			(29)	[1]
Fair Value, Inputs, Level 1 | Mutual And Exchange Traded Funds [Member] | Commodities Investment [Member]
Schedule Of Pension And Other Postretirment Plan Assets By Fair Value [Line Items]
Securities	(6)	[1]	(9)	[1]
Fair Value, Inputs, Level 1 | Debt Securities [Member]
Schedule Of Pension And Other Postretirment Plan Assets By Fair Value [Line Items]
Securities	(3)	[1]	(13)	[1]
Fair Value, Inputs, Level 1 | Debt Securities [Member] | US Treasury Securities [Member]
Schedule Of Pension And Other Postretirment Plan Assets By Fair Value [Line Items]
Securities	(3)	[1]	(13)	[1]
Fair Value, Inputs, Level 2
Schedule Of Pension And Other Postretirment Plan Assets By Fair Value [Line Items]
Securities	(136)	[1]
Fair Value, Inputs, Level 2 | Mutual And Exchange Traded Funds [Member]
Schedule Of Pension And Other Postretirment Plan Assets By Fair Value [Line Items]
Securities	(121)	[1]
Fair Value, Inputs, Level 2 | Mutual And Exchange Traded Funds [Member] | International Fund [Member]
Schedule Of Pension And Other Postretirment Plan Assets By Fair Value [Line Items]
Securities	(43)	[1]
Fair Value, Inputs, Level 2 | Mutual And Exchange Traded Funds [Member] | Domestic Fund [Member]
Schedule Of Pension And Other Postretirment Plan Assets By Fair Value [Line Items]
Securities	(41)	[1]
Fair Value, Inputs, Level 2 | Mutual And Exchange Traded Funds [Member] | Debt Fund [Member]
Schedule Of Pension And Other Postretirment Plan Assets By Fair Value [Line Items]
Securities	(20)	[1]
Fair Value, Inputs, Level 2 | Mutual And Exchange Traded Funds [Member] | Alternative Strategies Fund [Member]
Schedule Of Pension And Other Postretirment Plan Assets By Fair Value [Line Items]
Securities	(17)	[1]
Fair Value, Inputs, Level 2 | Debt Securities [Member]
Schedule Of Pension And Other Postretirment Plan Assets By Fair Value [Line Items]
Securities	(15)	[1]	(24)	[1]
Fair Value, Inputs, Level 2 | Debt Securities [Member] | Mortgage-backed Securities, Issued by US Government Sponsored Enterprises
Schedule Of Pension And Other Postretirment Plan Assets By Fair Value [Line Items]
Securities	(13)	[1]	(21)	[1]
Fair Value, Inputs, Level 2 | Debt Securities [Member] | Non Agency Residential Mortgage Backed Securities [Member]
Schedule Of Pension And Other Postretirment Plan Assets By Fair Value [Line Items]
Securities	(2)	[1]	(2)	[1]
Fair Value, Inputs, Level 2 | Debt Securities [Member] | Corporate Bond Securities [Member]
Schedule Of Pension And Other Postretirment Plan Assets By Fair Value [Line Items]
Securities			$ (1)	[1],[3]

[1] For further information on fair value hierarchy levels, see Note 1.

[2] Includes holdings in Bancorp common stock.

[3] Includes private label asset backed securities.