Goodwill (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Dec. 31, 2014
Changes in carrying amounts of goodwill
Balance at the beginning of the period	$ 432,888
Foreign currency translation	(357)
Balance at the end of the period	432,531
Region One
Changes in carrying amounts of goodwill
Balance at the beginning of the period	161,222
Foreign currency translation	(357)
Balance at the end of the period	160,865
Region Two
Changes in carrying amounts of goodwill
Balance at the beginning of the period		141,512
Balance at the end of the period	141,512	141,512
Region Three
Changes in carrying amounts of goodwill
Balance at the beginning of the period		36,389
Balance at the end of the period	36,389	36,389
Region Four
Changes in carrying amounts of goodwill
Balance at the beginning of the period		62,664
Balance at the end of the period	62,664	62,664
Region Five
Changes in carrying amounts of goodwill
Balance at the beginning of the period		31,101
Balance at the end of the period	$ 31,101	$ 31,101