Share-Based Compensation - Nonvested Options (Details) - Nonvested Option Shares - $ / shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Nonvested Awards, Number of Shares [Roll Forward]
Nonvested awards, beginning balance (in shares)	108,750	81,750	76,500
Granted (in shares)	36,000	66,000	42,000
Vested (in shares)	(42,000)	(28,875)	(36,750)
Canceled (in shares)	0	(10,125)	0
Nonvested awards, ending balance (in shares)	102,750	108,750	81,750
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Exercise Price [Roll Forward]
Nonvested options, beginning balance (in dollars per share)	$ 46.65	$ 47.21	$ 47.99
Granted (in dollars per share)	35.70	46.75	42.56
Vested (in dollars per share)	47.66	48.46	43.52
Canceled (in dollars per share)	0	46.66	0
Nonvested options, ending balance (in dollars per share)	$ 42.40	$ 46.65	$ 47.21