Stock-Based Compensation - Stock Options Activity Rollforward (Details) (USD $)	12 Months Ended
	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Outstanding options, beginning of year, number of shares	2,523,593
Granted, number of shares	0
Exercised, number of shares	(739,290)
Forfeited, number of shares	(5,893)
Expired, number of shares	(30,378)
Outstanding options, end of year, number of shares	1,748,032
Outstanding options exercisable, end of year, number of shares	1,393,010
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Roll Forward]
Outstanding options, beginning of year, weighted average exercise price	$ 17.20
Granted, weighted average exercise price	$ 0.00
Exercised, weighted average exercise price	$ 17.73
Forfeited, weighted average exercise price	$ 12.85
Expired, weighted average exercise price	$ 16.20
Outstanding options, end of year, weighted average exercise price	$ 17.01
Outstanding options exercisable, end of year, weighted average exercise price	$ 17.15
Outstanding options, end of year weighted average remaining contractual term	4 years 5 months 4 days
Outstanding options exercisable, end of year, weighted average remaining contractual term	4 years 1 month 13 days