Share Incentive Plans, Stock Option Activity (Details) - 2006 and 2015 Plans [Member] - Stock Options [Member] - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2020
Stock Option Shares [Roll Forward]
Outstanding, beginning balance (in shares)	711,060	696,716	696,716
Granted (in shares)	100,000		155,000
Exercised (in shares)	(74,615)		(135,146)
Forfeited (in shares)	(850)		(5,510)
Outstanding, ending balance (in shares)	735,595		711,060
Weighted Average Exercise Price [Abstract]
Outstanding, beginning balance (in dollars per share)	$ 19.58	$ 18.13	$ 18.13
Granted (in dollars per share)	51.75		14.85
Exercised (in dollars per share)	5.70		6.37
Forfeited (in dollars per share)	21.63		27.25
Outstanding, ending balance (in dollars per share)	25.36		19.58
Weighted Average Grant Date Fair Value [Abstract]
Outstanding, beginning balance (in dollars per share)	6.42	$ 6.17	6.17
Granted (in dollars per share)	13.77		4.41
Exercised (in dollars per share)	2.66		2.74
Forfeited (in dollars per share)	6.15		8.64
Outstanding, ending balance (in dollars per share)	$ 7.80		$ 6.42
Intrinsic value of options exercised	$ 3.3	$ 0.9