Subsequent Events (Details) - USD ($)	Oct. 25, 2017	Sep. 30, 2017	Apr. 20, 2016	Jan. 21, 2015
Subsequent Event [Line Items]
Stock repurchase program, remaining authorized repurchase amount		$ 173,700,000
October Twenty Six Two Thousand Ten Program [Member]
Subsequent Event [Line Items]
Stock repurchase program, authorized amount			$ 1,000,000,000.0	$ 2,400,000,000
October Twenty Six Two Thousand Ten Program [Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Stock repurchase program, authorized amount	$ 1,000,000,000.0