Stockholder's Equity - Quarterly (Details) - USD ($)		3 Months Ended		9 Months Ended
	May 19, 2015	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018	Mar. 10, 2014
Equity, Class of Stock [Line Items]
Preferred stock dividends declared		$ 1,698,000	$ 1,698,000	$ 5,094,000	$ 5,094,000
Convertible Preferred Stock, Shares Issued upon Conversion	38.0619
Convertible Preferred Stock, Threshold Percentage of Stock Price Trigger				150.00%
Treasury Stock, Shares [Roll Forward]
Treasury stock, shares, beginning of period				15,336,871
Purchase of treasury stock, shares				1,440,396
Treasury stock, shares, end of period		17,462,976		17,462,976
Treasury stock, cost, beginning of period				$ 234,142,000
Shares purchased for minimum tax withholding under the Equity Plan or other similar transactions				22,420,000	8,544,000
Purchase of treasury stock, cost				22,420,000
Treasury stock, cost, end of period		$ 266,882,000		$ 266,882,000
Treasury stock, average cost per share, beginning of period, in dollars per share				$ 15.27
Purchase of treasury stock, average cost per share, in dollars per share				15.57
Treasury stock, average cost per share, end of period, in dollars per share		$ 15.28		$ 15.28
Embedded Cash Conversion Option			1,000	$ (596,000)	28,974,000
Treasury Stock
Treasury Stock, Shares [Roll Forward]
Shares purchased for minimum tax withholding under the Equity Plan or other similar transactions				674,792
Treasury stock shares received, other				10,917
Shares purchased for minimum tax withholding under the Equity Plan or other similar transactions				$ 10,153,000
Treasury stock received, value, other				$ 167,000
Shares purchased for minimum tax withholding under the Equity Plan or other similar transactions, Average Cost Per Share				$ 15.05
Treasury stock received, per share, other				$ 15.34
Call Option
Equity, Class of Stock [Line Items]
Option indexed to Issuer's Equity, Value	$ 15,900,000
Minimum
Equity, Class of Stock [Line Items]
Convertible Preferred Stock, Threshold Consecutive Trading Days				20 days
Minimum | Call Option
Equity, Class of Stock [Line Items]
Option Indexed to Issuer's Equity, Strike Price				$ 26.27
Maximum
Equity, Class of Stock [Line Items]
Convertible Preferred Stock, Threshold Consecutive Trading Days				30 days
Maximum | Call Option
Equity, Class of Stock [Line Items]
Option Indexed to Issuer's Equity, Strike Price				$ 33.54
Convertible Preferred Stock
Equity, Class of Stock [Line Items]
Preferred stock issuance, net of issuance costs, shares	120,750
Preferred Stock, Dividend Rate, Percentage				5.625%
Proceeds from Issuance of Preferred Stock, net of issuance costs				$ 117,200,000
Adjustments to Additional Paid in Capital, Stock Issued, Issuance Costs				3,600,000
Preferred Stock, Liquidation Preference Per Share	$ 1,000
Convertible Preferred Stock | Retained Earnings/(Accumulated deficit)
Equity, Class of Stock [Line Items]
Preferred stock dividends declared		$ 1,698,000	1,698,000	5,094,000	$ 5,094,000
Convertible Debt
Treasury Stock, Shares [Roll Forward]
Convertible debt, unamortized discount		$ 16,000,000		16,000,000		$ 19,500,000
2022 convertible note | Convertible Debt
Treasury Stock, Shares [Roll Forward]
Purchase of treasury stock, cost				$ 19,500,000
Convertible debt, unamortized discount							$ 23,400,000
Embedded Cash Conversion Option			$ 28,973,000