Net Income Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Numerator:
Net income attributable to common stockholders (numerator for basic net income per share)	$ 20,919	$ 22,995	$ 55,008	$ 47,656
Net income allocated to participating securities	(20)	(30)	(55)	(61)
Numerator for basic net income per share	20,899	22,965	54,953	47,595
Numerator for diluted net income per share	$ 24,758	$ 26,824	$ 62,671	$ 55,313
Denominator:
Denominator for basic net income per share - weighted average outstanding common shares	97,989	95,913	97,424	95,782
Dilutive effect of contingently issuable shares	54	0	553	3
Denominator for diluted net income per share	126,943	123,465	126,659	123,227
Net income per share attributable to common stockholders - basic	$ 0.21	$ 0.24	$ 0.56	$ 0.50
Net income per share attributable to common stockholders - diluted	$ 0.20	$ 0.22	$ 0.49	$ 0.45
Equity Option [Member]
Denominator:
Dilutive effect of stock options	1,571	222	1,353	112
Series A Preferred Stock [Member]
Numerator:
Dividends on Preferred Stock, paid and unpaid	$ 1,750	$ 1,750	$ 3,500	$ 3,500
Denominator:
Dilutive effect of Preferred Stock	10,602	10,602	10,602	10,602
Series B Preferred Stock [Member]
Numerator:
Dividends on Preferred Stock, paid and unpaid	$ 2,109	$ 2,109	$ 4,218	$ 4,218
Denominator:
Dilutive effect of Preferred Stock	16,727	16,728	16,727	16,728