Fair Value (Fair Value of the 2019 Notes and 2021 Notes) (Details) - Senior Notes - Level 2 - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Senior Unsecured Notes due 2019
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Estimated fair value of senior unsecured notes	$ 293,000	$ 312,000
Senior Unsecured Notes due 2021
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Estimated fair value of senior unsecured notes	$ 194,000	$ 213,000

The fair value amount of long-term debt whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission.

No definition available.

Name:	us-gaap_LongTermDebtFairValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant