Revolving Credit Facility and Long-Term Debt Revolving Credit Facility and Long-Term Debt (Details) (USD $) In Millions, unless otherwise specified									12 Months Ended
	Dec. 31, 2011 Wells Fargo Credit Agreement [Member]	Dec. 31, 2011 Wells Fargo Credit Agreement [Member] Fixed 30 Day Interest Rate 1 [Member]	Dec. 31, 2010 Wells Fargo Credit Agreement [Member] Fixed 30 Day Interest Rate 1 [Member]	Dec. 31, 2011 Wells Fargo Credit Agreement [Member] Fixed 30 Day Interest Rate 2 [Member]	Dec. 31, 2011 Wells Fargo Credit Agreement [Member] Swingline Variable Interest Rate [Member]	Dec. 31, 2010 Wells Fargo Credit Agreement [Member] Swingline Variable Interest Rate [Member]	Dec. 31, 2009 Wells Fargo Credit Agreement [Member] Fixed Interest Rate Swap Agreement [Member]	Dec. 31, 2010 Bank of America Line Of Credit [Member]	Dec. 31, 2011 Line of Credit [Member] Wells Fargo Credit Agreement [Member] Borrower's Option 1 [Member]	Dec. 31, 2011 Line of Credit [Member] Wells Fargo Credit Agreement [Member] Borrower's Option 2 [Member]	Dec. 31, 2011 Line of Credit [Member] Wells Fargo Credit Agreement [Member] Borrower's Option 3 [Member]	Dec. 31, 2011 Line of Credit [Member] Wells Fargo Credit Agreement [Member] Default Option [Member]	Dec. 31, 2011 Line of Credit [Member] Wells Fargo Credit Agreement [Member] Base Rate Option 1 [Member]	Dec. 31, 2011 Line of Credit [Member] Wells Fargo Credit Agreement [Member] Base Rate Option 2 [Member]	Dec. 31, 2011 Line of Credit [Member] Wells Fargo Credit Agreement [Member] Base Rate Option 3 [Member]
Line of Credit Facility [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	$ 125.0							$ 30.0
Debt Instrument, Basis Spread on Variable Rate									0.25%	1.25%	1.25%	1.25%		0.50%	1.00%
Debt Instrument, Description of Variable Rate Basis									base rate	London Inter-Bank Offered Rate (“LIBOR”) Market Index Rate	LIBOR Rate	LIBOR Market Index Rate	prime rate (as announced by Wells Fargo)	federal funds rate	LIBOR for an interest period of one month
Line of Credit Facility, Amount Outstanding	30.7	24.0	22.0	5.0	1.7	4.5	55.0
Line of Credit Facility, Remaining Borrowing Capacity	$ 94.3
Debt Instrument, Interest Rate, Stated Percentage		1.54%	1.52%	1.55%	1.84%	1.56%	2.73%