Repurchase Agreements (Details) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2017 USD ($) Security	Dec. 31, 2016 USD ($) Security
Repurchase Agreements [Abstract]
Repurchase agreements outstanding	$ 773,300	$ 594,600
Weighted average of remaining maturities days	78 days	65 days
Repurchase Agreement Characteristics Remaining Maturities [Abstract]
Less than one month, repurchase agreements	$ 149,363	$ 60,690
One to three months, repurchase agreements	269,063	456,502
Greater than three months, repurchase agreements	354,891	77,423
Total repurchase agreements	$ 773,317	$ 594,615
Repurchase Agreement Characteristics, Weighted Average Rates [Abstract]
Less than one month, weighted average rate	1.04%	1.14%
One to three months, weighted average rate	0.98%	0.91%
Greater than three months, weighted average rate	1.08%	0.90%
Weighted average rate	1.04%	0.93%
Number of overnight or demand securities | Security	0	0