Summary of Significant Accounting Policies (Details 8) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Carrying Reported Amount Fair Value Disclosure [Member]
Financial assets:
Cash and cash equivalents	$ 251,299	$ 292,995
Carrying Reported Amount Fair Value Disclosure [Member] | Senior Secured Credit Facility [Member]
Financial liabilities:
Long-term debt	735,110	748,777
Carrying Reported Amount Fair Value Disclosure [Member] | Senior Unsecured Notes [Member]
Financial liabilities:
Long-term debt	300,000	300,000
Estimate Of Fair Value Fair Value Disclosure [Member]
Financial assets:
Cash and cash equivalents	251,299	292,995
Estimate Of Fair Value Fair Value Disclosure [Member] | Senior Secured Credit Facility [Member]
Financial liabilities:
Long-term debt	735,628	748,150
Estimate Of Fair Value Fair Value Disclosure [Member] | Senior Unsecured Notes [Member]
Financial liabilities:
Long-term debt	$ 284,250	$ 297,000