Fair Value Measurements (Details 1) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Beginning and ending balances for the Company's fair value measurements using Level 3 inputs
Other comprehensive income	$ (33,414)	[1]	$ 24,198	[1]	$ (2,289)
Deferred income tax liability	136,166		120,082
2014
Beginning and ending balances for the Company's fair value measurements using Level 3 inputs
Asset, Beginning Balance	25,720		17,220
Unrealized (losses) gains included in other comprehensive income	(12,420)		8,500
Asset, Ending Balance	13,300		25,720
Restatement Adjustment
Beginning and ending balances for the Company's fair value measurements using Level 3 inputs
Other comprehensive income	4,400
Non-current assets	7,000
Deferred income tax liability	$ 2,600

[1] All amounts are net of tax. Amounts in parentheses indicate debits