Stockholders' Equity and Equity Compensation Plans (Details Textual) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Dec. 31, 2014
Stockholders Equity And Equity Compensation Plans [Line Items]
Remaining number of shares available for repurchase	4,200,000
Repurchase of common stock for employee tax withholdings, shares	110,000	157,000
Repurchase of common stock for tax withholdings, value	$ 5,200	$ 7,600
Cash dividends declared per common share	$ 0.25	$ 0.235
Cash dividend	$ 8,200	$ 7,700
Stock warrants term			10 years
Stock warrants, exercise price	$ 26.68		$ 26.68
Stock-based compensation expense	$ 5,395	4,857
Performance Shares
Stockholders Equity And Equity Compensation Plans [Line Items]
Performance based awards granted to executive management and certain key employees shares	100,000
Vesting maturity date	first quarter of 2023
Vesting period	2 years
Restricted common stock
Stockholders Equity And Equity Compensation Plans [Line Items]
Vesting period	4 years
Separation Agreement
Stockholders Equity And Equity Compensation Plans [Line Items]
Stock-based compensation expense	$ 5,400	$ 4,900
Comcast
Stockholders Equity And Equity Compensation Plans [Line Items]
Issuance of stock warrants			2,900,000
Stock warrants issued	1,000,000.0
Stock warrants vested	0
SEC Rule 10b5-1 Plan
Stockholders Equity And Equity Compensation Plans [Line Items]
Repurchase of common stock, shares	142,000	142,000
Total amount paid	$ 6,500	$ 6,400
Weighted-average price per share	$ 45.94	$ 45.26