SOI Proceeds from sales (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Investments, Debt and Equity Securities [Abstract]
Proceeds from sales	$ 2,705,999	[1]	$ 2,518,568	[1]	$ 2,697,809	[1]
Gross realized gains from sales	47,852		71,758		113,984
Gross realized losses from sales	$ 1,229		$ 27,792		$ 4,371

[1] Includes gains (losses) on the hedged asset for fair value hedges.