Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Net income	$ 38,101	$ 32,589	$ 31,697	$ 65,038
Undistributed Earnings (Loss) Allocated to Participating Securities, Basic	178	401	221	825
Net earnings available to common shareholders	$ 37,923	$ 32,188	$ 31,476	$ 64,213
Weighted-average outstanding shares of common stock - basic	46,850,944	47,727,786	47,235,859	47,644,729
Dilutive effect of equity incentive plans	0	64,291	20,037	76,652
Incremental Common Shares Attributable to Dilutive Effect of Contingently Issuable Shares	586,611	1,310,802	1,023,521	1,085,111
Weighted-average outstanding shares of common stock - diluted	47,437,555	49,102,879	48,279,417	48,806,492
Basic	$ 0.81	$ 0.67	$ 0.67	$ 1.35
Diluted	$ 0.80	$ 0.66	$ 0.65	$ 1.32
Share options excluded from the computation of diluted earnings per share	0	0	0	0