Goodwill and Intangible Assets Rollforward (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
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)	$ (26,593)	$ (27,486)	$ (27,180)
Goodwill [Member]
Goodwill And Intangible Assets [Line Items]
Balance at January 1				456,380				456,380	456,380	456,380
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				152,254				179,740	152,254	179,740
Amortization of intangible assets									(26,593)	(27,486)
Balance at December 31	125,661				152,254				125,661	152,254	179,740
Indefinite Lived Intangible Assets [Member]
Goodwill And Intangible Assets [Line Items]
Balance at January 1				7,350				7,350	7,350	7,350
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				$ 159,604				$ 187,090	159,604	187,090
Amortization of intangible assets									(26,593)	(27,486)
Balance at December 31	$ 133,011				$ 159,604				$ 133,011	$ 159,604	$ 187,090