Stock Based Compensation - Stock Compensation Plans (Details) - $ / shares	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Stock Options Outstanding
Stock options outstanding, number of shares, balance (in shares)	695,000
Stock options outstanding, granted (in shares)	0	0
Stock options exercised, exercised (in shares)	(1,000)
Stock options outstanding, forfeited/expired (in shares)	0
Stock options outstanding, number of shares, balance (in shares)	694,000
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)	$ 22.42
Stock options, weighted average exercise price, granted (in dollars per share)	0
Stock options, weighted average exercise price, exercised (in dollars per share)	10.65
Stock options, weighted average exercise price, forfeited/expired (in dollars per share)	0
Stock options, weighted average exercise price, balance (in dollars per share)	$ 22.43
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)	694,000
Stock options outstanding, weighted average exercise price, exercisable (in dollars per share)	$ 22.43
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)	72,000
Non-vested shares outstanding, granted (in shares)	0
Non-vested shares outstanding, vested (earned) (in shares)	(29,000)
Non-vested shares outstanding, forfeited/expired (in shares)	(2,000)
Non-vested shares outstanding, balance (in shares)	41,000
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 grant-date fair value, balance (in dollars per share)	$ 21.45
Non-vested shares outstanding. weighted-average grant-date fair value, granted (in dollars per share)	0
Non-vested shares outstanding. weighted-average grant-date fair value, vested (earned) (in dollars per share)	19.34
Non-vested shares outstanding. weighted-average grant-date fair value, forfeited/expired (in dollars per share)	21.82
Non-vested shares outstanding. weighted-average grant-date fair value, balance (in dollars per share)	$ 22.90
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)	817,000
Non-vested shares outstanding, granted (in shares)	483,000
Non-vested shares outstanding, vested (earned) (in shares)	(300,000)
Non-vested shares outstanding, forfeited/expired (in shares)	(83,000)
Non-vested shares outstanding, balance (in shares)	917,000
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 grant-date fair value, balance (in dollars per share)	$ 27.65
Non-vested shares outstanding. weighted-average grant-date fair value, granted (in dollars per share)	26.25
Non-vested shares outstanding. weighted-average grant-date fair value, vested (earned) (in dollars per share)	26.44
Non-vested shares outstanding. weighted-average grant-date fair value, forfeited/expired (in dollars per share)	28.39
Non-vested shares outstanding. weighted-average grant-date fair value, balance (in dollars per share)	$ 27.28