Fair Value (Details 2) - Interest rate options - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Assets (Liabilities):
Balance at the beginning of the period	$ 2,702	$ 31,463	$ 4,371	$ 63,471
Total gains or losses (realized/unrealized):
Included in earnings (or changes in net assets)	2,013	(12,928)	344	(44,936)
Balance at the end of the period	$ 4,715	$ 18,535	$ 4,715	$ 18,535