Earnings per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended							9 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2021	Sep. 30, 2020
Net income	$ 11,114	$ 18,330	$ 13,850	$ 17,665	$ 12,338	$ 1,952	$ 63,722	$ 43,294	$ 78,012
Less income allocated to non-controlling interests	(92)				(121)			(271)	(292)
Less income allocated to participating securities:
Non-forfeitable dividends on participating securities	(113)				(103)			(346)	(294)
Income allocated to participating securities									(45)
Total net income allocated to participating securities	(113)				(103)			(346)	(339)
Net income available to common stockholders	10,909				12,114			42,677	77,381
Net income for diluted net income per share	$ 10,909				$ 12,114			$ 42,677	$ 77,381
Reconciliation of shares
Shares for basic net income per share	39,177,000				39,061,000			39,149,000	39,218,000
Effect of dilutive securities:
Total effect of dilutive securities (in shares)					51,000				51,000
Shares for diluted net income per share	39,177,000				39,112,000			39,149,000	39,269,000
Basic net income per share (in dollars per share)	$ 0.28				$ 0.31			$ 1.09	$ 1.97
Diluted net income per share (in dollars per share)	$ 0.28				$ 0.31			$ 1.09	$ 1.97
Performance-based stock units
Effect of dilutive securities:
Stock options and performance-based stock units (in shares)					51,000				51,000
Performance-based stock units would be earned based on TSR targets	0							0