Debt Credit Facility (Details) (USD $) In Thousands, unless otherwise specified	9 Months Ended			9 Months Ended
	Sep. 30, 2014 U.S. revolving credit facility [Member] Long-term Debt [Member]	Sep. 30, 2014 U.S. letter of credit [Member]	Sep. 30, 2014 U.S. letter of credit [Member] Long-term Debt [Member]	Sep. 30, 2014 Iceland revolving line of credit [Member] Long-term Debt [Member]	Sep. 30, 2014 Short-term Debt [Member] Iceland revolving line of credit [Member]		Dec. 31, 2013 Short-term Debt [Member] Iceland revolving line of credit [Member]
Line of Credit Facility [Line Items]
Credit facility face amount	$ 150,000			$ 50,000
Credit facility maximum amount	148,560			50,000
Borrowing availability	76,327			50,000
Outstanding borrowings	0			0	0	[1],[2]	6,000	[1],[2]
Letter of credit sub-facility amount		80,000	80,000
Outstanding letters of credit issued			$ 72,233
Credit facility term	5 years			3 years

[1] Borrowings under the Iceland revolving credit facility bear variable interest based on LIBOR plus the applicable margin per annum. The interest rate at December 31, 2013 was 3.92%.

[2] These items are recorded in accrued and other current liabilities based on the repayment terms and expected maturity.