Common Stock Repurchase Plan (Narrative) (Details) - USD ($)					9 Months Ended		26 Months Ended
	Oct. 08, 2018	Aug. 02, 2018	Oct. 30, 2017	Jul. 29, 2016	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Jul. 31, 2018
Equity Class Of Treasury Stock [Line Items]
Shares repurchase program, repurchased cost					$ 226,100,000	$ 75,400,000
Accelerated Share Repurchase [Member] | Deutsche Bank AG [Member]
Equity Class Of Treasury Stock [Line Items]
Shares repurchase program, expiration date					Oct. 08, 2018
Pre payment of repurchase program		$ 150,000,000
Repurchase program, Shares		1,766,004
Percentage of accelerated share repurchase		80.00%
Accelerated Share Repurchase [Member] | Deutsche Bank AG [Member] | Subsequent Event [Member]
Equity Class Of Treasury Stock [Line Items]
Accelerated share repurchase remaining shares returned	389,825
Common Stock [Member]
Equity Class Of Treasury Stock [Line Items]
Shares repurchase program, authorized amount								$ 700,000,000
Shares repurchase program, expiration date				Jul. 31, 2018
Stock repurchase program, additional authorized amount			$ 250,000,000					$ 300,000,000
Shares repurchase program, extended expiration date			Oct. 31, 2020
Shares repurchase program, shares repurchased					3,567,733	1,757,747
Common Stock [Member] | Share Repurchase Program Excluding ASR [Member]
Equity Class Of Treasury Stock [Line Items]
Shares repurchase program, shares repurchased					3,600,000		6,500,000
Shares repurchase program, repurchased cost					$ 226,000,000		$ 350,200,000
Shares repurchase program, average price per share					$ 63.35		$ 53.68
Common Stock [Member] | Maximum [Member]
Equity Class Of Treasury Stock [Line Items]
Shares repurchase program, authorized amount				$ 150,000,000