Allowance for Credit Losses (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Dec. 31, 2016
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans and Leases Receivable, Allowance	$ 970		$ 1,142		$ 970	$ 1,142
Total recorded investment					9,478,578	9,179,404
Allowance for Loan and Lease Losses [Roll Forward]
Balance, beginning of period			1,142
Balance, end of period	970		970
Conventional Loan [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Allowance for Credit Losses, Collectively Evaluated for Impairment					970	1,142
Allowance for Credit Losses, Individually Evaluated for Impairment					0	0
Loans and Leases Receivable, Allowance	880	$ 1,483	1,142	$ 1,686	970	1,142
Recorded Investment, Collectively Evaluated for Impairment					9,109,542	8,772,681
Recorded Investment, Individually Evaluated for Impairment					9,648	9,889
Total recorded investment					$ 9,119,190	$ 8,782,570
Allowance for Loan and Lease Losses [Roll Forward]
Balance, beginning of period	880	1,483	1,142	1,686
Allowance for Loan and Lease Losses Write-offs, Net	90	(266)	(172)	(469)
Balance, end of period	$ 970	$ 1,217	$ 970	$ 1,217