Stock-Based Compensation (Details) - USD ($) $ / shares in Units, $ in Thousands		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award
Stock-based compensation expense recognized		$ 5,276	$ 6,108	$ 4,817
Unrecognized Compensation Cost		$ 2,760
Expiration date of 2007 Stock Incentive Plan		May 20, 2024
Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award
Stock-based compensation expense recognized		$ 5,061	$ 5,931	$ 4,603
Unrecognized Compensation Cost		$ 2,760
Weighted Average Remaining Amortization Periods		9 months 18 days
Number of units [Abstract]
Balance (in shares)		842,000	904,000	986,000
Granted (in shares)		272,000	314,000	252,000
Vested (in shares)	[1]	(308,000)	(361,000)	(334,000)
Cancelled or forfeited (in shares)		(13,000)	(15,000)	0
Balance (in shares)		793,000	842,000	904,000
Expected to vest (in shares)		793,000	842,000	904,000
Weighted Average Grant-date Fair Value per Unit [Abstract]
Beginning balance, Weighted average grant-date fair value (in dollars per share)		$ 17.93	$ 14.77	$ 13.34
Granted, Weighted average grant-date fair value (in dollars per share)		18.30	19.85	18.90
Vested, Weighted average grant-date fair value (in dollars per share)	[1]	15.70	11.70	13.67
Cancelled or forfeited, Weighted average grant date fair value (in dollars per share)		19.06	17.71	0
Ending balance, Weighted average grant-date fair value (in dollars per share)		$ 18.90	$ 17.93	$ 14.77
Phantom Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award
Stock-based compensation expense recognized		$ 215	$ 177	$ 214
Unrecognized Compensation Cost		$ 0
Weighted Average Remaining Amortization Periods		0 years
Number of units [Abstract]
Balance (in shares)		183,000	170,000	157,000
Granted (in shares)		10,000	10,000	10,000
Dividend equivalents issued (in shares)		5,000	3,000	3,000
Balance (in shares)		198,000	183,000	170,000
Weighted Average Grant-date Fair Value per Unit [Abstract]
Granted, Weighted average grant-date fair value (in dollars per share)		$ 21.49	$ 17.72	$ 21.35
Performance Vested Restricted Stock Units [Member] | Scheduled to Vest January 1, 2021 [Member]
Number of units [Abstract]
Balance (in shares)	[2]	141,000
Expected to vest (in shares)	[2]	141,000
Not expected to vest (in shares)	[2]	0
Performance Vested Restricted Stock Units [Member] | Scheduled to Vest January 1, 2022 [Member]
Number of units [Abstract]
Balance (in shares)		174,000
Expected to vest (in shares)		174,000
Not expected to vest (in shares)		0
Performance Vested Restricted Stock Units [Member] | Scheduled to Vest January 1, 2023 [Member]
Number of units [Abstract]
Balance (in shares)		152,000
Expected to vest (in shares)		152,000
Not expected to vest (in shares)		0
2007 Stock Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award
Maximum number of shares authorized under restricted stock, unrestricted stock, RSU's and stock options to officers, employees and non-employee directors (in shares)		6,500,000
Exercisable (in shares)
Available for future grants (in shares)		2,307,000

[1] The number of RSUs vested includes shares that the Company withheld on behalf of employees to satisfy statutory tax withholding requirements.

[2] The performance vesting criteria for the performance-based RSUs with a vesting date of January 1, 2021 were achieved.