Net Income (Loss) Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Numerator:
Net income (loss) attributable to common stockholders	$ (6,527)	$ 20,919	$ 1,086	$ 55,008
Net income allocated to participating securities	6	(20)	(1)	(55)
Numerator for basic net income (loss) per share	(6,521)	20,899	1,085	54,953
Numerator for diluted net income (loss) per share	$ (6,521)	$ 24,758	$ 1,085	$ 62,671
Denominator:
Denominator for basic net income (loss) per share - weighted average outstanding common shares (in shares)	111,111	97,989	105,927	97,424
Dilutive effect of contingently issuable shares (in shares)	0	54	1,131	553
Denominator for diluted net income per share (in shares)	111,111	126,943	109,405	126,659
Net income (loss) per share attributable to common stockholders - basic (in dollars per share)	$ (0.06)	$ 0.21	$ 0.01	$ 0.56
Net income (loss) per share attributable to common stockholders - diluted (in dollars per share)	$ (0.06)	$ 0.20	$ 0.01	$ 0.49
Equity Option
Denominator:
Dilutive effect of stock options (in shares)	0	1,571	2,347	1,353
Series A Preferred Stock
Numerator:
Preferred Stock Dividends, Income Statement Impact	$ 0	$ 1,750	$ 0	$ 3,500
Denominator:
Dilutive effect of Preferred Stock (in shares)	0	10,602	0	10,602
Preferred Stock Dividends, Anti-Dilutive, Excluded			$ 4,600
Cumulative unpaid preferred stock dividends		$ 1,800		$ 1,800
Series B Preferred Stock
Numerator:
Preferred Stock Dividends, Income Statement Impact	$ 0	$ 2,109	$ 0	$ 4,218
Denominator:
Dilutive effect of Preferred Stock (in shares)	0	16,727	0	16,727
Preferred Stock Dividends, Anti-Dilutive, Excluded			$ 16,700
Cumulative unpaid preferred stock dividends	$ 2,100	$ 2,100	$ 2,100	$ 2,100
Employee Stock Option
Denominator:
Antidilutive securities excluded from computation of diluted earnings per share	300		300	100
Unvested Performance Based Restricted Stock Units
Denominator:
Antidilutive securities excluded from computation of diluted earnings per share	700	100	600	600
Unvested Non-Performance-Based Restricted Stock Units
Denominator:
Antidilutive securities excluded from computation of diluted earnings per share		1,800		1,600