Stock Based Compensation RSU Rollforward (Details) - RSUs [Member] - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
RSU Rollforward [Line Items]
Unvested RSUs Outstanding	678,803	748,180
RSU Awards Granted	354,393
Vested	(411,593)
Forfeited	(12,177)
Weighted Average Grant Date Fair Value (RSUs)	$ 32.98	$ 27.73	$ 23.36
Weighted Average Grant Date Fair Value of RSU's Granted During the Period	37.28	$ 29.98	$ 25.38
Weighted Average Grant Date Fair Value of Vested RSUs	27.15
Weighted Average Grant Date Fair Value of RSUs forfeited	$ 32.35
RSU Compensation expense recognized	$ 12,100	$ 11,000	$ 11,900
RSUs unrecognized compensation expense	$ 6,500
RSUs unrecognized compensation expense, weighted average recognition period	1 year 8 months 12 days
RSUs Aggregate Intrinsic Value, Vested	$ 15,400	$ 17,700	$ 18,300

Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

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