Stock-Based Compensation Plans (Restricted Stock Units) (Details) - $ / shares shares in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Performance Shares [Member]
Changes to non-vested restricted stock and restricted stock units
Non-vested, beginning balance, shares	0.0	0.3	1.0
Non-vested, beginning balance, weighted average fair value at date of grant	$ 0.00	$ 12.90	$ 12.69
Granted, shares	0.3	0.0	0.1
Granted, weighted average fair value at date of grant	$ 21.84	$ 0.00	$ 16.34
Vested, shares	0.0	(0.3)	(0.8)
Vested, weighted average fair value at date of grant	$ 0.00	$ 12.90	$ 13.32
Forfeited, shares	0.0	0.0	0.0
Forfeited, weighted average fair value at date of grant	$ 0.00	$ 0.00	$ 0.00
Non-vested, ending balance, shares	0.3	0.0	0.3
Non-vested, ending balance, weighted average fair value at date of grant	$ 21.84	$ 0.00	$ 12.90
Time-Based Restricted Stock [Member]
Changes to non-vested restricted stock and restricted stock units
Non-vested, beginning balance, shares	1.3	1.4	1.6
Non-vested, beginning balance, weighted average fair value at date of grant	$ 17.66	$ 14.62	$ 13.04
Granted, shares	0.7	0.7	0.6
Granted, weighted average fair value at date of grant	$ 22.41	$ 20.55	$ 16.35
Vested, shares	(0.5)	(0.6)	(0.7)
Vested, weighted average fair value at date of grant	$ 16.53	$ 14.33	$ 12.75
Forfeited, shares	(0.2)	(0.2)	(0.1)
Forfeited, weighted average fair value at date of grant	$ 20.78	$ 18.85	$ 14.09
Non-vested, ending balance, shares	1.3	1.3	1.4
Non-vested, ending balance, weighted average fair value at date of grant	$ 20.20	$ 17.66	$ 14.62
Restricted Stock Units (RSUs) [Member]
Changes to non-vested restricted stock and restricted stock units
Non-vested, ending balance, shares	2.2