Stockholder's Equity - Quarterly (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended		12 Months Ended
	May 19, 2015	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2014
Equity, Class of Stock [Line Items]
Preferred stock dividends declared		$ 1,698	$ 1,698
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		12,133,276
Purchase of treasury stock, shares		539,800
Treasury stock, shares, end of period		13,129,110
Treasury stock, cost, beginning of period		$ 186,846
Shares purchased for minimum tax withholding under the Equity Plan or other similar transactions		4,910	4,455
Purchase of treasury stock, cost		7,584		$ 300
Treasury stock, cost, end of period		$ 200,915
Treasury stock, average cost per share, beginning of period, in dollars per share		$ 15.40
Purchase of treasury stock, average cost per share, in dollars per share		14.05
Treasury stock, average cost per share, end of period, in dollars per share		$ 15.30
Treasury Stock
Treasury Stock, Shares [Roll Forward]
Shares purchased for minimum tax withholding under the Equity Plan or other similar transactions		343,795
Shares purchased for minimum tax withholding under the Equity Plan or other similar transactions		$ 4,910
Shares purchased for minimum tax withholding under the Equity Plan or other similar transactions, Average Cost Per Share		$ 14.28
Treasury stock shares received, other		112,239
Treasury stock received, value, other		$ 1,575
Treasury stock received, per share, other		$ 14.03
Call Option
Equity, Class of Stock [Line Items]
Option indexed to Issuer's Equity, Value	$ 15,900
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
Proceeds from Issuance of Preferred Stock, net of issuance costs			117,200
Adjustments to Additional Paid in Capital, Stock Issued, Issuance Costs		$ 3,600
Preferred Stock, Dividend Rate, Percentage		5.625%
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	$ 1,698