Share-Based Compensation - Nonqualified Stock Option Transactions (Details) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($) $ / shares shares
Number of Options
Options outstanding beginning balance (in shares) | shares	486
Expired (in shares) | shares	(254)
Options outstanding ending balance (in shares) | shares	232
Exercisable at the end of the year (in shares) | shares	232
Weighted Average Exercise Price
Options outstanding beginning balance (in dollars per share) | $ / shares	$ 31.77
Expired (in dollars per share) | $ / shares	37.78
Options outstanding ending balance (in dollars per share) | $ / shares	25.19
Exercisable at the end of the year (in dollars per share) | $ / shares	$ 25.19
Weighted average remaining contractual term of options outstanding ending balance (in years)	9 months	[1]
Weighted average remaining contractual term of options exercisable at the end of the year (in years)	9 months	[1]
Aggregate intrinsic value of options outstanding at the end of the year | $	$ 513	[2]
Aggregate intrinsic value of options exercisable at the end of the year | $	$ 513	[2]

[1] Represents the average remaining contractual life in years.

[2] Aggregate intrinsic value represents the total pre-tax intrinsic value that would have been received by the option holders if they had exercised their options on December 31, 2017. Intrinsic value equals the difference between the Company's average of the high and low stock price on the last trading day of the year and the option exercise price, multiplied by the number of shares. This amount will fluctuate with changes in the fair value of the Company's common stock.