Stock-Based Compensation - Stock Options Activity Rollforward (Details)	12 Months Ended
	Dec. 31, 2015 $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Outstanding options, beginning of year, number of shares | shares	1,748,032
Exercised, number of shares | shares	(350,438)
Forfeited, number of shares | shares	(10,216)
Outstanding options, end of year, number of shares | shares	1,387,378
Outstanding options exercisable, end of year, number of shares | shares	1,265,596
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 | $ / shares	$ 17.01
Exercised, weighted average exercise price | $ / shares	16.77
Forfeited, weighted average exercise price | $ / shares	16.82
Outstanding options, end of year, weighted average exercise price | $ / shares	17.06
Outstanding options exercisable, end of year, weighted average exercise price | $ / shares	$ 17.05
Outstanding options, end of year weighted average remaining contractual term	3 years 8 months 6 days
Outstanding options exercisable, end of year, weighted average remaining contractual term	3 years 7 months 22 days