Income Taxes (Summary of Changes in Gross Amount of Unrecognized Tax Benefits) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Income Taxes
Balance as of January 1,	$ 51,004	$ 45,800	$ 36,710	$ 33,570
Addition based on tax positions related to the current year		8,100	7,308	5,138
Addition based on tax positions related to prior years		1,301	4,060
Payments related to settled items		(451)
Reduction due to lapse of statute of limitations (with 2013 estimate)	(6,900)	(3,746)	(2,278)	(1,998)
Balance as of December 31,		$ 51,004	$ 45,800	$ 36,710