Summary of Significant Accounting Policies - Loans Receivable and Allowance for Loan Losses (Details)	12 Months Ended
	Dec. 31, 2016
Accounting Policies [Abstract]
Period past due when a loan is deemed a troubled debt restructuring	90 days
Period past maturity when loans are still considered as current	30 days
Period past maturity when loans are classified as past due	60 days
Period during which borrower is required to demonstrate performance	6 months
Extended prior period over which loss experience factors are evaluated	3 years
Length of period one over which the historical loss experience is analyzed	12 months
Length of period two over which the historical loss experience is analyzed	15 months
Length of period three over which the historical loss experience is analyzed	18 months
Length of period four over which the historical loss experience is analyzed	24 months
Minimum length of period over which the historical loss experience is analyzed for a particular loan type	2 years