Debt (Details Textual) (USD $) In Millions, unless otherwise specified	Mar. 31, 2015
Line of Credit Facility [Line Items]
Notes payable, agreement amount	$ 30.0
Notes payable	61.5
Notes payable, due 2040
Line of Credit Facility [Line Items]
Notes payable, agreement amount	14.0
Interest rate of debt instruments	5.00%
Notes payable, due 2030
Line of Credit Facility [Line Items]
Notes payable, agreement amount	16.0
Interest rate of debt instruments	4.50%
Line of credit
Line of Credit Facility [Line Items]
Total borrowing capacity under lines of credit	878.1
Total available for borrowings under lines of credit	538.6
Line of credit | Secured Debt
Line of Credit Facility [Line Items]
Total borrowing capacity under lines of credit	$ 28.1