Employee Stock Benefit Plans (Stock Appreciation Right Activity) (Details) - Stock Appreciation Rights (SARs) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding [Roll Forward]
Outstanding balance at beginning of period	244,229	244,229	244,229
Granted	26,839	0	0
Exercised	(7,060)
Canceled	(240,829)
Outstanding balance at end of period	23,179	244,229	244,229	244,229
Exercisable balance at end of period	19,999
Share-based Compensation Arrangement by Share-based Payment Award, Non-Option Equity Instruments, Outstanding, Weighted Average Exercise Price [Roll Forward]
Outstanding, weighted-average exercise price, balance at beginning of period (in USD per share)	$ 21.27	$ 21.27	$ 21.27
Granted, weighted-average exercise price (in USD per share)	17.19
Exercised, weighted-average exercise price (in USD per share)	7.16
Canceled, weighted-average exercise price (in USD per share)	21.29
Outstanding, weighted-average exercise price, balance at end of period (in USD per share)	$ 20.66	$ 21.27	$ 21.27	$ 21.27
Outstanding, weighted-average remaining contractual life	5 years 2 months 12 days	1 month 6 days	8 years	9 years
Outstanding, aggregate intrinsic value	$ 0	$ 4	$ 14	$ 2,483
Share-based Compensation Arrangement by Share-based Payment Award, Other than Options, Exercises in Period, Intrinsic Value	$ 56
Share-based Compensation Arrangement By Share-based Payment Award, Non-option Equity Instruments, Exercisable, Weighted Average Exercise Price	$ 20.29
Share-based compensation arrangement by share-based payment award, non-option equity instruments, exercisable, weighted average remaining contractual life	5 years
Share-based Compensation Arrangement By Share-based Payment Award, Non-option Equity Instruments, Exercisable, Intrinsic Value	$ 0