Retirement and Benefit Plans (Plan Assets Measured at Fair Value on a Recurring Basis) (Detail) - USD ($) $ in Millions		Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan Disclosure
Securities	[1]	$ 172	$ 166
Equity securities
Defined Benefit Plan Disclosure
Securities	[1],[2]	56	52
Mutual and exchange-traded funds
Defined Benefit Plan Disclosure
Securities	[1]	97	101
Mutual and exchange-traded funds | Money market funds
Defined Benefit Plan Disclosure
Securities	[1]	6	15
Mutual and exchange-traded funds | International funds
Defined Benefit Plan Disclosure
Securities	[1]	31	35
Mutual and exchange-traded funds | Domestic funds
Defined Benefit Plan Disclosure
Securities	[1]	39	31
Mutual and exchange-traded funds | Debt funds
Defined Benefit Plan Disclosure
Securities	[1]	5	3
Mutual and exchange-traded funds | Alternative strategies
Defined Benefit Plan Disclosure
Securities	[1]	10	11
Mutual and exchange-traded funds | Commodity funds
Defined Benefit Plan Disclosure
Securities	[1]	6	6
Debt securities
Defined Benefit Plan Disclosure
Securities	[1]	19	13
Debt securities | U.S. Treasury and federal agencies securities
Defined Benefit Plan Disclosure
Securities	[1]	8	4
Debt securities | Agency mortgage-backed securities | Residential mortgage-backed securities
Defined Benefit Plan Disclosure
Securities	[1]	1	3
Debt securities | Agency mortgage-backed securities | Commercial mortgage-backed securities
Defined Benefit Plan Disclosure
Securities	[1]	2	2
Debt securities | Non-agency mortgage-backed securities | Commercial mortgage-backed securities
Defined Benefit Plan Disclosure
Securities	[1]		1
Debt securities | Asset-backed securities and other debt securities
Defined Benefit Plan Disclosure
Securities	[1],[3]	8	3
Fair value level 1
Defined Benefit Plan Disclosure
Securities	[1]	76	75
Fair value level 1 | Equity securities
Defined Benefit Plan Disclosure
Securities	[1],[2]	56	52
Fair value level 1 | Mutual and exchange-traded funds
Defined Benefit Plan Disclosure
Securities	[1]	13	21
Fair value level 1 | Mutual and exchange-traded funds | Money market funds
Defined Benefit Plan Disclosure
Securities	[1]	6	15
Fair value level 1 | Mutual and exchange-traded funds | Alternative strategies
Defined Benefit Plan Disclosure
Securities	[1]	1	0
Fair value level 1 | Mutual and exchange-traded funds | Commodity funds
Defined Benefit Plan Disclosure
Securities	[1]	6	6
Fair value level 1 | Debt securities
Defined Benefit Plan Disclosure
Securities	[1]	7	2
Fair value level 1 | Debt securities | U.S. Treasury and federal agencies securities
Defined Benefit Plan Disclosure
Securities	[1]	7	2
Fair value level 2
Defined Benefit Plan Disclosure
Securities	[1]	96	91
Fair value level 2 | Mutual and exchange-traded funds
Defined Benefit Plan Disclosure
Securities	[1]	84	80
Fair value level 2 | Mutual and exchange-traded funds | International funds
Defined Benefit Plan Disclosure
Securities	[1]	31	35
Fair value level 2 | Mutual and exchange-traded funds | Domestic funds
Defined Benefit Plan Disclosure
Securities	[1]	39	31
Fair value level 2 | Mutual and exchange-traded funds | Debt funds
Defined Benefit Plan Disclosure
Securities	[1]	5	3
Fair value level 2 | Mutual and exchange-traded funds | Alternative strategies
Defined Benefit Plan Disclosure
Securities	[1]	9	11
Fair value level 2 | Debt securities
Defined Benefit Plan Disclosure
Securities	[1]	12	11
Fair value level 2 | Debt securities | U.S. Treasury and federal agencies securities
Defined Benefit Plan Disclosure
Securities	[1]	1	2
Fair value level 2 | Debt securities | Agency mortgage-backed securities | Residential mortgage-backed securities
Defined Benefit Plan Disclosure
Securities	[1]	1	3
Fair value level 2 | Debt securities | Agency mortgage-backed securities | Commercial mortgage-backed securities
Defined Benefit Plan Disclosure
Securities	[1]	2	2
Fair value level 2 | Debt securities | Non-agency mortgage-backed securities | Commercial mortgage-backed securities
Defined Benefit Plan Disclosure
Securities	[1]		1
Fair value level 2 | Debt securities | Asset-backed securities and other debt securities
Defined Benefit Plan Disclosure
Securities	[1],[3]	$ 8	$ 3

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

[2] Includes holdings in Bancorp common stock.

[3] Includes corporate bonds.