Share Repurchase Programs (Details) shares in Millions, $ in Billions		3 Months Ended	4 Months Ended		6 Months Ended
	Jan. 05, 2015 USD ($) shares	Jun. 30, 2015 USD ($) shares	May. 05, 2015	May. 01, 2015 shares	Jun. 30, 2015 USD ($) shares	Jan. 02, 2015 USD ($)	Dec. 15, 2014 USD ($)	Dec. 17, 2013 USD ($)
Equity, Class of Treasury Stock [Line Items]
Remaining authorized repurchase amount		$ 9.8			$ 9.8
Repurchase Program 2014 [Member]
Equity, Class of Treasury Stock [Line Items]
Maximum authorization under share repurchase program							$ 10.0
Remaining authorized repurchase amount		$ 9.8			$ 9.8
Repurchase Program 2013 [Member]
Equity, Class of Treasury Stock [Line Items]
Maximum authorization under share repurchase program								$ 6.0
Repurchase of common stock (in shares) | shares		12.1			28.9
Value of stock repurchased in the period		$ 0.9			$ 2.9
Remaining authorized repurchase amount		$ 0.0			$ 0.0
January 2, 2015 [Member]
Equity, Class of Treasury Stock [Line Items]
Amount under ASR agreement entered into with JP Morgan Chase						2.0
Accelerated share repurchase, initial number of shares repurchased | shares	16.8
Accelerated share repurchase, final number of shares delivered | shares				3.1
Accelerated share repurchases percentage of notional purchase price			20.00%
Notional purchase price (as a percent)	80.00%
Accelerated share repurchases, initial treasury stock transaction	$ 1.6
Forward Contract Indexed to Issuer's Equity, Contract Reclassification			0.4