Financial Instruments (Details 3) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Investments, Debt and Equity Securities [Abstract]
Proceeds from maturities and sales	$ 2,387,900	$ 625,400	$ 3,363,374	$ 1,942,871
Realized gains	700	0	1,300	400
Realized losses	$ (2,000)	$ (100)	$ (2,900)	$ (300)