Earnings Per Share Attributable to Stockholders (Computation of Basic and Diluted Earnings Per Share) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Earnings Per Share Attributable to Stockholders [Abstract]
Basic, Net income attributable to stockholders	$ 10,377	$ 29,406
Diluted, Net income attributable to stockholders	$ 10,404	$ 29,406
Basic, WA number of shares	106,851,595	106,917,280
Effect of dilutive securities: PSUs, WA number of shares	263,557
Effect of dilutive securities: Stock options, WA number of shares	673,797	241,730
Diluted, WA number of shares	107,788,949	107,159,010
Basic, Per share amount	$ 0.10	$ 0.28
Effect of dilutive securities: Stock options, Per share amount		(0.01)
Diluted, Per share amount	$ 0.10	$ 0.27