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, 2016	Mar. 31, 2015
Earnings Per Share Attributable to Stockholders [Abstract]
Basic, Net income attributable to stockholders	$ 29,406	$ 23,777
Diluted, Net income attributable to stockholders	$ 29,406	$ 23,777
Basic, shares	106,917,280	107,484,944
Effect of dilutive securities: Stock options, shares	241,730	323,004
Diluted, shares	107,159,010	107,807,948
Basic, Per share amount	$ 0.28	$ 0.22
Effect of dilutive securities: Stock options, Per share amount	(0.01)
Diluted, Per share amount	$ 0.27	$ 0.22