Stock-Based Compensation Plans - Nonqualified Stock Options (Details) - Nonqualified Stock Options $ / shares in Units, shares in Millions, $ in Millions	6 Months Ended
	Jun. 30, 2016 USD ($) $ / shares shares
Change in options outstanding
Options granted (in shares) | shares	1.1
Assumptions used to estimate fair value of stock options granted during period
Weighted-average expected volatility (as a percent)	31.70%
Weighted-average expected term	6 years 6 months
Weighted-average risk-free interest rate (as a percent)	1.50%
Weighted-average expected dividend yield (as a percent)	4.07%
Weighted-average estimated fair value of stock options granted (in dollars per share) | $ / shares	$ 8.91
Other nonqualified stock option disclosures
Unrecognized compensation costs | $	$ 7.7
Weighted-average service period over which unrecognized compensation costs will be recognized	1 year 7 months 6 days