Long-term Debt Narrative (Details) (USD $)	3 Months Ended		9 Months Ended				9 Months Ended	0 Months Ended	9 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012	Sep. 30, 2013 Revolving Credit Facility [Member]	Sep. 30, 2013 Revolving Credit Facility, Prior to Fifth Amendment [Member]	May 30, 2013 Revolving Credit Facility, Fifth Amendment [Member]	Sep. 30, 2013 Revolving Credit Facility, Fifth Amendment [Member]	May 30, 2013 Revolving Credit Facility, Fifth Amendment [Member] Maximum [Member]	Sep. 30, 2013 LIBOR or CDOR [Member] Revolving Credit Facility, Prior to Fifth Amendment [Member] Minimum [Member]	Sep. 30, 2013 LIBOR or CDOR [Member] Revolving Credit Facility, Prior to Fifth Amendment [Member] Maximum [Member]	Sep. 30, 2013 LIBOR or CDOR [Member] Revolving Credit Facility, Fifth Amendment [Member] Minimum [Member]	Sep. 30, 2013 LIBOR or CDOR [Member] Revolving Credit Facility, Fifth Amendment [Member] Maximum [Member]
Debt Instrument [Line Items]
Revolving credit facility						$ 200,000,000
Revolving credit facility, potentially additional borrowing capacity						100,000,000
Revolving credit facility, basket for permitted stock repurchases, total								50,000,000
Revolving credit facility, basket for permitted stock repurchases in any year										15,000,000
Revolving credit facility, ceiling for dividends allowable amount								75,000,000
Revolving credit facility, description of variable rate basis							LIBOR or CDOR		LIBOR or CDOR
Revolving credit facility, margin added to variable interest rate											1.75%	2.25%	1.25%	1.75%
Revolving credit facility, amendment fees								300,000
Revolving credit facility, average borrowings	15,000,000	3,300,000	30,200,000	22,800,000
Revolving credit facility, minimum amount borrowed			0	0
Revolving credit facility, maximum amount borrowed			112,000,000	91,500,000
Revolving credit facility, weighted-average interest rate	1.70%	2.60%	1.90%	2.10%
Revolving credit facility and letter of credit, unused facility/participation fees	200,000	300,000	700,000	700,000
Amortization of debt issuance costs	100,000	100,000	300,000	300,000
Unamortized debt issuance costs	$ 1,500,000		$ 1,500,000		$ 1,500,000