Stock-Based Compensation - Unvested Performance Stock Awards (Details) - Performance Stock Awards - USD ($)	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Number of Shares
Balance (in shares)	136,271	121,656	168,453
Granted (in shares)	53,685	72,273	40,722
Vested (in shares)	(37,456)	(31,507)	(81,840)
Added by performance factor (in shares)	0	3,688	0
Non-vesting (in shares)	0	(12,689)	0
Forfeited (in shares)	(2,589)	(17,150)	(5,679)
Balance (in shares)	149,911	136,271	121,656
Weighted Average Grant Date Fair Value
Balance, weighted average grant date fair value (in dollars per share)	$ 37.87	$ 36.82	$ 0
Granted, weighted average grant date fair value (in dollars per share)	35.90	34.26	44.56
Vested, weighted average grant date fair value (in dollars per share)	36.79	29.38	16.40
Added by performance factor (in dollars per share)	0	30.45	0
Non-vesting, Weighted average grant date fair value (in dollars per share)	0	27.13	0
Forfeited, weighted average grant date fair value (in dollars per share)	39.72	37.15	28.79
Balance, weighted average grant date fair value (in dollars per share)	$ 37.60	$ 37.87	$ 36.82
Cash in lieu of fractional shares		$ 39