Stock Compensation - Summary of Transactions of Stock Option Plans (Details) - Stock Options - $ / shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Weighted-average exercise price
Options granted (in dollars per share)	$ 14.38	$ 13.58
Omnibus Incentive Plan
Number of shares
Beginning balance (in shares)	384,258	369,612	406,640
Options granted (in shares)	55,223	42,302	49,510
Options exercised (in shares)	(53,198)	(27,656)	(86,538)
Options forfeited (in shares)	0	0	0
Ending balance (in shares)	386,283	384,258	369,612
Exercisable options (in shares)	239,043	242,522	210,940
Weighted-average exercise price
Beginning balance (in dollars per share)	$ 23.75	$ 22.35	$ 20.90
Options granted (in dollars per share)	36.75	33.98	28.33
Options exercised (in dollars per share)	22.83	20.59	18.98
Ending balance (in dollars per share)	25.74	23.75	22.35
Exercisable options (in dollars per share)	$ 21.59	$ 21.01	$ 20.48
Omnibus Incentive Plan | Price range $ 18.08 — $ 18.30
Number of shares
Ending balance (in shares)	101,270
Weighted-average exercise price
Ending balance (in dollars per share)	$ 18.15
Price range - minimum (in dollars per share)	18.08
Price range - maximum (in dollars per share)	$ 18.30
Weighted-average contractual life	4 years
Omnibus Incentive Plan | Price range $ 19.21 — $ 27.18
Number of shares
Ending balance (in shares)	140,322
Weighted-average exercise price
Ending balance (in dollars per share)	$ 23.54
Price range - minimum (in dollars per share)	19.21
Price range - maximum (in dollars per share)	$ 27.18
Weighted-average contractual life	4 years 3 months 6 days
Omnibus Incentive Plan | Price range $ 28.33 — $ 38.55
Number of shares
Ending balance (in shares)	144,691
Weighted-average exercise price
Ending balance (in dollars per share)	$ 33.18
Price range - minimum (in dollars per share)	28.33
Price range - maximum (in dollars per share)	$ 38.55
Weighted-average contractual life	8 years 2 months 12 days