Debt (Narrative) (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended
	Sep. 30, 2013
Line of Credit Facility [Line Items]
Letters of credit	$ 33.5
Line of credit facility, interest rate during period	1.28%
Credit facility interest rate premium over fed funds rate, percentage	0.50%
Credit facility interest rate premium over LIBOR rate, percentage	1.00%
Margin for LIBOR based loans, percentage	1.10%
Margin for base rate loans, percentage	0.10%
Line of credit facility commitment fee amount, percentage	0.15%
Covenant ratio debt EBITDA maximum numerator, through June 30, 2014	3.25
Covenant ratio debt EBITDA maximum denominator, through June 30, 2014	1.00
Covenant Ratio Debt EBITDA Maximum Numerator, Thereafter	3.00
Covenant Ratio Debt EBITDA Maximum Denominator Thereafter	1.00
Covenant ratio coverage maximum numerator	4.00
Covenant ratio coverage maximum denominator	1.00
Office Lease Obligations [Member]
Line of Credit Facility [Line Items]
Letters of credit	$ 11.3