Fair Value Measurements (Details 2) (USD $) In Thousands	Jun. 30, 2011	Dec. 31, 2010
Fair value of long-term debt estimated using quoted market prices or discounted future cash flows
Fair value of long-term debt and interest rate contracts	$ 311,886	$ 307,865
Fair value in excess of carrying value	$ 3,926	$ 4,359

Estimated fair value of the debt instrument at the balance-sheet date.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 107
-Paragraph 10

Name:	us-gaap_DebtInstrumentFairValue
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant