Compensation Plans - Schedule of Employee Stock Options and SSARs Activity (Details) - Stock Options and SSARs	12 Months Ended
	Dec. 31, 2017 USD ($) $ / shares shares
Shares
Outstanding at beginning of period (in shares) | shares	270,246
Granted (in shares) | shares	0
Exercised (in shares) | shares	(164,116)
Forfeited (in shares) | shares	0
Outstanding at end of period (in shares) | shares	106,130
Exercisable (in shares) | shares	106,130
Weighted Average Exercise Price
Outstanding at beginning of period (usd per share) | $ / shares	$ 18.85
Granted (usd per share) | $ / shares	0.00
Exercised (usd per share) | $ / shares	22.40
Forfeited (usd per share) | $ / shares	0.00
Outstanding at end of period (usd per share) | $ / shares	13.37
Exercisable (usd per share) | $ / shares	$ 13.37
Additional Disclosures
Outstanding, weighted average remaining contractual term	1 year 11 months
Exercisable, weighted average remaining contractual term	1 year 11 months
Outstanding, aggregate intrinsic value | $	$ 3,373
Exercisable, aggregate intrinsic value | $	$ 3,373