Condensed Consolidated Statements of Comprehensive Income (unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Statement of Comprehensive Income [Abstract]
Net income allocated to common stockholders	$ 19,628	$ 9,419	$ 23,985	$ 17,022
Currency translation adjustment, net of tax	(3,070)	1,793	960	(5,246)
Comprehensive income allocated to common stockholders	$ 16,558	$ 11,212	$ 24,945	$ 11,776