Equity Incentive Plans (Options by Exercise Price) (Details) - $ / shares shares in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Granted, Wtd. Avg. grant date fair value (in dollars per share)	$ 5.91	$ 2.09	$ 4.26
Options granted, shares	462	300	300
Exercise prices and related information of stock option outstanding
Options outstanding, number outstanding (in shares)	1,230
Options outstanding, Wtd. Avg. remaining contractual life	7 years 3 months 30 days
Options outstanding, Wtd. Avg. exercise price (in dollars per share)	$ 25.02
Options exercisable, Number exercisable (in shares)	523
Options exercisable Wtd. Avg. Remaining Contractual Life	5 years 10 months 35 days
Options exercisable, Wtd. Avg. exercise price (in dollars per share)	$ 22.04
0-18.23
Exercise prices and related information of stock option outstanding
Lower range limit, Exercise price (in dollars per share)	0
Upper range limit, Exercise price (in dollars per share)	$ 18.23
Options outstanding, number outstanding (in shares)	185
Options outstanding, Wtd. Avg. remaining contractual life	3 years 2 months 20 days
Options outstanding, Wtd. Avg. exercise price (in dollars per share)	$ 13.97
Options exercisable, Number exercisable (in shares)	185
Options exercisable Wtd. Avg. Remaining Contractual Life	3 years 2 months 20 days
Options exercisable, Wtd. Avg. exercise price (in dollars per share)	$ 13.97
18.24-22.26
Exercise prices and related information of stock option outstanding
Lower range limit, Exercise price (in dollars per share)	18.24
Upper range limit, Exercise price (in dollars per share)	$ 22.26
Options outstanding, number outstanding (in shares)	392
Options outstanding, Wtd. Avg. remaining contractual life	7 years 5 months 38 days
Options outstanding, Wtd. Avg. exercise price (in dollars per share)	$ 20.18
Options exercisable, Number exercisable (in shares)	133
Options exercisable Wtd. Avg. Remaining Contractual Life	6 years 9 months 63 days
Options exercisable, Wtd. Avg. exercise price (in dollars per share)	$ 20.62
22.27-29.39
Exercise prices and related information of stock option outstanding
Lower range limit, Exercise price (in dollars per share)	22.27
Upper range limit, Exercise price (in dollars per share)	$ 29.39
Options outstanding, number outstanding (in shares)	233
Options outstanding, Wtd. Avg. remaining contractual life	6 years 11 months 38 days
Options outstanding, Wtd. Avg. exercise price (in dollars per share)	$ 28.77
Options exercisable, Number exercisable (in shares)	120
Options exercisable Wtd. Avg. Remaining Contractual Life	6 years 8 months 74 days
Options exercisable, Wtd. Avg. exercise price (in dollars per share)	$ 28.77
29.40-43.15
Exercise prices and related information of stock option outstanding
Lower range limit, Exercise price (in dollars per share)	32.41
Upper range limit, Exercise price (in dollars per share)	$ 43.15
Options outstanding, number outstanding (in shares)	420
Options outstanding, Wtd. Avg. remaining contractual life	9 years 43 days
Options outstanding, Wtd. Avg. exercise price (in dollars per share)	$ 32.27
Options exercisable, Number exercisable (in shares)	85
Options exercisable Wtd. Avg. Remaining Contractual Life	8 years 9 months 70 days
Options exercisable, Wtd. Avg. exercise price (in dollars per share)	$ 32.27