Stock-Based Compensation - Other Stock Option Information (Details) - $ / shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Shares
Options outstanding (in shares)	115,246	185,023	290,853
Expired (in shares)	0	(250)	0
Exercised (in shares)	(64,645)	(69,527)	(105,830)
Options outstanding (in shares)	50,601	115,246	185,023
Weighted Average Exercise Price
Options outstanding (in dollars per share)	$ 20.73	$ 21.04	$ 20.88
Expired (in dollars per share)	0.00	22.00	0.00
Exercised (in dollars per share)	22.65	21.55	20.61
Options outstanding (in dollars per share)	18.28	20.73	21.04
Weighted Average Grant Date Fair Value
Options outstanding (in dollars per share)	4.86	4.88	4.85
Expired (in dollars per share)	0.00	4.90	0.00
Exercised (in dollars per share)	5.00	4.91	7.32
Options outstanding (in dollars per share)	$ 4.68	$ 4.86	$ 4.88