Long-term Debt (Details) (USD $) In Thousands, unless otherwise specified	1 Months Ended	12 Months Ended
	Nov. 30, 2011	Dec. 31, 2013	Dec. 31, 2012
Line of Credit Facility [Line Items]
Weighted average interest rate of long-term bank debt (in hundredths)		2.30%	2.20%
Syndicated Senior Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Borrowing capacity	$ 250,000
Term of revolving credit facility	5 years
Expiration date of revolving credit facility	Nov. 30, 2016
Variable rate of credit facility		LIBOR
Outstanding credit facility		$ 79,250	$ 64,000
Syndicated Senior Revolving Credit Facility [Member] | Minimum [Member]
Line of Credit Facility [Line Items]
Basis spread (in hundredths)		1.75%
Syndicated Senior Revolving Credit Facility [Member] | Maximum [Member]
Line of Credit Facility [Line Items]
Basis spread (in hundredths)		2.50%