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, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Sep. 30, 2019	Sep. 30, 2018
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Income attributable to common stockholders		$ 33,597	$ 35,699	$ 20,350	$ 35,858	$ 40,405	$ 15,359	$ 89,646	$ 91,622
Weighted average common shares outstanding, basic (in shares)		66,685			67,329			66,681	67,246
Weighted average common shares outstanding, diluted (in shares)		67,361			67,896			67,240	67,743
Basic income per common share (in dollars per share)		$ 0.50			$ 0.53			$ 1.34	$ 1.36
Diluted income per common share (in dollars per share)		$ 0.50			$ 0.53			$ 1.33	$ 1.35
Restricted stock units [Member]
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Stock based payment arrangements (in shares)	[1]	544			399			450	321
Stock options [Member]
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Stock based payment arrangements (in shares)		132			166			109	155
Restricted stock [Member]
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Stock based payment arrangements (in shares)		0			2			0	21

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