Employee Benefit Plans (Pension Plan Assets Fair Value Hierarchy) (Details) - PNC Pension Plan - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 5,253	$ 4,617	$ 4,316
Cash
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	11	45
Money Market Funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	339	404
US government and agency securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	338	285
Corporate Debt
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	583	580
Common Stock
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	804	652
Mutual Fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	271
Other
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	77	60
Investments measured at net asset value
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2,830	2,591
Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1,374	1,242
Level 1 | Cash
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	10	35
Level 1 | Money Market Funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	339	404
Level 1 | US government and agency securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	233	158
Level 1 | Common Stock
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	791	645
Level 1 | Other
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1
Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1,037	776
Level 2 | Cash
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1	10
Level 2 | US government and agency securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	105	127
Level 2 | Corporate Debt
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	578	572
Level 2 | Common Stock
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	13	7
Level 2 | Mutual Fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	271
Level 2 | Other
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	69	60
Level 3
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	12	8
Level 3 | Corporate Debt
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	5	$ 8
Level 3 | Other
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 7