Goodwill and Intangible Assets Rollforward (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Goodwill And Intangible Assets [Line Items]
Amortization of intangible assets	$ (6,000)	$ (7,000)	$ (7,000)	$ (7,000)	$ (6,000)	$ (7,000)	$ (7,000)	$ (7,000)	$ (27,486)	$ (27,180)	$ (31,799)
Goodwill [Member]
Goodwill And Intangible Assets [Line Items]
Balance at December 31	456,380				456,380				456,380	456,380	456,380
Definite Lived Intangible Assets [Member]
Goodwill And Intangible Assets [Line Items]
Balance at January 1				179,740				206,920	179,740	206,920
Amortization of intangible assets									(27,486)	(27,180)
Balance at December 31	152,254				179,740				152,254	179,740
Indefinite Lived Intangible Assets [Member]
Goodwill And Intangible Assets [Line Items]
Balance at December 31	7,350				7,350				7,350	7,350	7,350
Total intangible assets [Member]
Goodwill And Intangible Assets [Line Items]
Balance at January 1				187,090				214,270	187,090	214,270
Amortization of intangible assets									(27,486)	(27,180)
Balance at December 31	$ 159,604				$ 187,090				$ 159,604	$ 187,090