Stock-Based Compensation - Summary of Information about Outstanding and Exercisable Stock Options (Details) (Non-qualified stock options, USD $) In Millions, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2014
Information about outstanding non-qualified stock options
Exercise price, low end of range (in dollars per share)	$ 7.83
Exercise price, high end of range (in dollars per share)	$ 43.01
Number of Options Outstanding	2.8
Weighted Average Remaining Life	4 years 11 months 12 days
Weighted average exercise price of options Outstanding (in dollars per share)	$ 19.12
Number of Options Exercisable (in shares)	2.3
Weighted average exercise price of options exercisable (in dollars per share)	$ 16.16
Range of exercise prices $7.83 - $10.90
Information about outstanding non-qualified stock options
Exercise price, low end of range (in dollars per share)	$ 7.83
Exercise price, high end of range (in dollars per share)	$ 10.90
Number of Options Outstanding	1.0
Weighted Average Remaining Life	4 years 7 months 6 days
Weighted average exercise price of options Outstanding (in dollars per share)	$ 9.41
Number of Options Exercisable (in shares)	1.0
Weighted average exercise price of options exercisable (in dollars per share)	$ 9.41
Range of exercise prices $14.51 - $21.11
Information about outstanding non-qualified stock options
Exercise price, low end of range (in dollars per share)	$ 14.51
Exercise price, high end of range (in dollars per share)	$ 21.11
Number of Options Outstanding	0.8
Weighted Average Remaining Life	4 years 7 months 17 days
Weighted average exercise price of options Outstanding (in dollars per share)	$ 19.29
Number of Options Exercisable (in shares)	0.8
Weighted average exercise price of options exercisable (in dollars per share)	$ 19.29
Range of exercise prices $22.00 - $43.01
Information about outstanding non-qualified stock options
Exercise price, low end of range (in dollars per share)	$ 22.00
Exercise price, high end of range (in dollars per share)	$ 43.01
Number of Options Outstanding	1.0
Weighted Average Remaining Life	5 years 6 months 15 days
Weighted average exercise price of options Outstanding (in dollars per share)	$ 28.58
Number of Options Exercisable (in shares)	0.5
Weighted average exercise price of options exercisable (in dollars per share)	$ 24.95