Fair Value Measurements - Quantitative Information, Level 3 (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2015	Dec. 31, 2014
Nonrecurring | Impaired Loans
Fair value measurements for financial instruments measured at fair value on a non-recurring basis
Impaired loans	$ 862	$ 1,908
Level 3
Fair value measurements for financial instruments measured at fair value on a non-recurring basis
Impaired loans	2,393,455	2,279,081
Level 3 | Nonrecurring | Impaired Loans
Fair value measurements for financial instruments measured at fair value on a non-recurring basis
Impaired loans	$ 862	$ 1,908
Valuation Technique(s)	Market approach	Market approach
Unobservable Input(s)	Adjustment for differences between the comparable sales	Adjustment for differences between the comparable sales
Level 3 | Nonrecurring | Impaired Loans | Minimum
Fair value measurements for financial instruments measured at fair value on a non-recurring basis
Range of Inputs; Weighted Average	(8.50%)	(47.50%)
Level 3 | Nonrecurring | Impaired Loans | Maximum
Fair value measurements for financial instruments measured at fair value on a non-recurring basis
Range of Inputs; Weighted Average	10.40%	96.20%
Level 3 | Nonrecurring | Impaired Loans | Weighted Average
Fair value measurements for financial instruments measured at fair value on a non-recurring basis
Range of Inputs; Weighted Average	0.95%	7.00%