Debt (Details Textual) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended	12 Months Ended
	Mar. 31, 2013	Dec. 31, 2012
Recourse | Corporate Revolving Credit Facility
Debt (Textual) [Abstract]
Revolving credit facility	$ 425.0
Maturity date of credit facility	Oct. 20, 2016
Used revolving credit facility for letters of credit	70.1
Availability of the revolving credit facility	354.9
Borrowing under revolving credit facility exclusive of letters of credit	0
Letter of credit expiring in current year	1.7
Credit facility, description of variable rate reference rate basis	Libor
Percentage points added to LIBOR to compute interest rates on the credit facility	1.50%
Credit facility, description of variable rate reference rate basis, alternative computation	prime
Percentage points added to prime to compute interest rates on the credit facility, alternative computation	0.50%
Recourse | Convertible Subordinated Notes
Debt (Textual) [Abstract]
Capital in excess of par value related to the convertible subordinated notes' conversion options	92.8	92.8
Date through which debt discount is being amortized	Jun. 01, 2018
Effective annual interest rate yield based upon the estimated market interest rate	8.42%
Conversion price of convertible subordinated notes (in dollars per share)	$ 51.04
Number of shares issuable in exchange of Convertible Subordinated Notes	8,816,614
Number of shares that would have been issued if the Convertible Subordinated Notes had been converted, in shares	0
Non-Recourse | TILC warehouse facility
Debt (Textual) [Abstract]
Revolving credit facility	475.0
Line of Credit Facility, Amount Outstanding	167.9
Availability of the revolving credit facility	$ 307.1
Interest at a defined index rate plus a margin for advances under the facility	2.22%
Maturity date	August 2013
Number of installments payable for amounts outstanding at maturity, absent renewal	3
Installment payable date, installment one	February 2014
Installment payable date, installment two	August 2014
Installment payable date, installment three	February 2015