Investments and Fair Value Measurements Fair Value Inputs, Quantitative Information (Details) (Significant Unobservable Inputs (Level 3), Fair Value, Measurements, Recurring, USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		12 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Warrants	$ 2,228		2,342
Fair value of derivatives embedded within convertible debt	162,039		169,386
Option Model [Member]
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Warrants	2,228		2,342
Discounted Cash Flow [Member]
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Fair value of derivatives embedded within convertible debt	$ 162,039		169,386
Warrants (1) | Option Model [Member]
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Stock price (dollars per share)	$ 3.86	$ 3.95
Exercise price (dollars per share)	$ 1.68	$ 1.68
Term (in years)	1 year 7 months 6 days	1 year 10 months 2 days
Volatility	41.45%	44.42%
Dividend rate	0.00%	0.00%
Risk-free return	0.70%	0.70%
Derivative Financial Instruments, Liabilities [Member] | Discounted Cash Flow [Member]
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Stock price (dollars per share)	$ 21.97	$ 21.31
Volatility	16.00%	16.00%
Assumed annual stock dividend	5.00%	5.00%
Assumed annual cash dividend (dollars per share)	$ 1.60	$ 1.60
Convertible trading price	107.25%	106.80%
Implied credit spread	7.00%		6.75%
Minimum [Member] | Derivative Financial Instruments, Liabilities [Member] | Discounted Cash Flow [Member]
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Implied credit spread	6.50%		6.25%
Maximum [Member] | Derivative Financial Instruments, Liabilities [Member] | Discounted Cash Flow [Member]
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Implied credit spread	7.50%		7.25%