Stock Based Compensation - Stock Compensation Plans (Details) - $ / shares	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Stock Options Outstanding
Stock options outstanding, number of shares, balance (in shares)	812,000
Stock options outstanding, granted (in shares)	0	0
Stock options exercised, exercised (in shares)	(111,000)
Stock options outstanding, forfeited/expired (in shares)	(6,000)
Stock options outstanding, number of shares, balance (in shares)	695,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Stock options, weighted average exercise price, balance (in dollars per share)	$ 21.98
Stock options, weighted average exercise price, granted (in dollars per share)	0.00
Stock options, weighted average exercise price, exercised (in dollars per share)	19.22
Stock options, weighted average exercise price, forfeited/expired (in dollars per share)	21.73
Stock options, weighted average exercise price, balance (in dollars per share)	$ 22.42
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Stock options outstanding, number of shares, exercisable (in shares)	661,000
Stock options outstanding, weighted average exercise price, exercisable (in dollars per share)	$ 22.37
Non-vested Stock Awards Outstanding
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Non-vested shares outstanding, balance (in shares)	162,000
Non-vested shares outstanding, granted (in shares)	0
Non-vested shares outstanding, vested (in shares)	(55,000)
Non-vested shares outstanding, forfeited (in shares)	(10,000)
Non-vested shares outstanding, balance (in shares)	97,000
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Non-vested shares outstanding. weighted-average exercise price, balance (in dollars per share)	$ 20.86
Non-vested shares outstanding. weighted-average exercise price, granted (in dollars per share)	0.00
Non-vested shares outstanding. weighted-average exercise price, vested (in dollars per share)	18.95
Non-vested shares outstanding. weighted-average exercise price, forfeited/expired (in dollars per share)	20.12
Non-vested shares outstanding. weighted-average exercise price, balance (in dollars per share)	$ 22.00
Non-vested Stock Units Outstanding
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Non-vested shares outstanding, balance (in shares)	652,000
Non-vested shares outstanding, granted (in shares)	343,000
Non-vested shares outstanding, vested (in shares)	(175,000)
Non-vested shares outstanding, forfeited (in shares)	(91,000)
Non-vested shares outstanding, balance (in shares)	729,000
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Non-vested shares outstanding. weighted-average exercise price, balance (in dollars per share)	$ 27.92
Non-vested shares outstanding. weighted-average exercise price, granted (in dollars per share)	29.31
Non-vested shares outstanding. weighted-average exercise price, vested (in dollars per share)	27.74
Non-vested shares outstanding. weighted-average exercise price, forfeited/expired (in dollars per share)	28.37
Non-vested shares outstanding. weighted-average exercise price, balance (in dollars per share)	$ 28.56