Earnings Per Common Share (Basic and Diluted EPS) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Income (loss) attributable to common stockholders									$ 119,738	$ 57,425	$ 30,880
Weighted average common shares outstanding, basic (in shares)									67,273	66,900	66,055
Weighted average common shares outstanding, diluted (in shares)									67,748	67,404	66,609
Basic EPS
Net income (loss) per share (in dollars per share)	$ 0.42	$ 0.53	$ 0.60	$ 0.23	$ 0.26	$ 0.28	$ 0.26	$ 0.06	$ 1.78	$ 0.86	$ 0.47
Diluted EPS
Net income (loss) per share (in dollars per share)	$ 0.41	$ 0.53	$ 0.60	$ 0.23	$ 0.26	$ 0.27	$ 0.26	$ 0.06	$ 1.77	$ 0.85	$ 0.46
Restricted stock [Member]
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Effect of dilutive securities									16	65	207
Restricted stock units [Member]
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Effect of dilutive securities									324	235	129
Stock options [Member]
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Effect of dilutive securities									135	204	218