Earnings Per Share (Basic and Diluted EPS) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		3 Months Ended						9 Months Ended
		Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2020	Sep. 30, 2019
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Income attributable to common stockholders		$ 44,895	$ 43,622	$ 22,029	$ 33,597	$ 35,699	$ 20,350	$ 110,546	$ 89,646
Weighted average common shares outstanding, basic (in shares)		67,141			66,685			67,001	66,681
Weighted average common shares outstanding, diluted (in shares)		67,967			67,361			67,725	67,240
Basic income per common share (in dollars per share)		$ 0.67			$ 0.50			$ 1.65	$ 1.34
Diluted income per common share (in dollars per share)		$ 0.66			$ 0.50			$ 1.63	$ 1.33
Restricted stock units [Member]
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Stock based payment arrangements (in shares)	[1]	682			544			602	450
Stock options [Member]
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Stock based payment arrangements (in shares)		144			132			122	109

[1] Includes service-based and contingently issuable performance-based restricted stock units.