Fair Value Measurements - Financial assets and liabilities measured at fair value on a recurring basis (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Level I [Member]
Assets:
U.S. Treasury securities	$ 39,779	$ 55,022
Mortgage-backed securities:
Interest rate cap	0	0
Liabilities:
Interest rate swaps	0	0
Level I [Member] | Interest rate cap [Member]
Mortgage-backed securities:
Interest rate cap	0
Level II [Member]
Assets:
U.S. Treasury securities	0	0
Mortgage-backed securities:
Interest rate cap	136	50
Liabilities:
Interest rate swaps	619	337
Level II [Member] | Interest rate cap [Member]
Mortgage-backed securities:
Interest rate cap	35
Level III [Member]
Assets:
U.S. Treasury securities	0	0
Mortgage-backed securities:
Interest rate cap	0	0
Liabilities:
Interest rate swaps	0	0
Level III [Member] | Interest rate cap [Member]
Mortgage-backed securities:
Interest rate cap	0
Recurring [Member]
Assets:
U.S. government agencies	67,717	41,397
Obligations of states and political subdivisions	76,569	57,740
Mortgage-backed securities:
Agency	141,684	173,213
Non-agency	14,882	28,123
Other asset backed securities	54,988	31,713
Corporate securities	16,889	16,077
Interest rate swaps	136	50
Liabilities:
Interest rate swaps	619	337
Recurring [Member] | Interest rate cap [Member]
Mortgage-backed securities:
Interest rate cap	35
Recurring [Member] | US Treasury Securities [Member]
Assets:
U.S. Treasury securities	50
Recurring [Member] | Level I [Member]
Assets:
U.S. government agencies	0	0
Obligations of states and political subdivisions	0	0
Mortgage-backed securities:
Agency	0	0
Non-agency	0	0
Other asset backed securities	0	0
Corporate securities	0	0
Interest rate swaps	0	0
Liabilities:
Interest rate swaps	0	0
Recurring [Member] | Level I [Member] | Interest rate cap [Member]
Mortgage-backed securities:
Interest rate cap	0
Recurring [Member] | Level I [Member] | US Treasury Securities [Member]
Assets:
U.S. Treasury securities	0
Recurring [Member] | Level II [Member]
Assets:
U.S. government agencies	67,717	41,397
Obligations of states and political subdivisions	76,569	57,740
Mortgage-backed securities:
Agency	141,684	173,213
Non-agency	14,882	28,123
Other asset backed securities	54,988	31,713
Corporate securities	16,889	16,077
Interest rate swaps	136	50
Liabilities:
Interest rate swaps	619	337
Recurring [Member] | Level II [Member] | Interest rate cap [Member]
Mortgage-backed securities:
Interest rate cap	35
Recurring [Member] | Level II [Member] | US Treasury Securities [Member]
Assets:
U.S. Treasury securities	50
Recurring [Member] | Level III [Member]
Assets:
U.S. government agencies	0	0
Obligations of states and political subdivisions	0	0
Mortgage-backed securities:
Agency	0	0
Non-agency	0	0
Other asset backed securities	0	$ 0
Corporate securities	0
Interest rate swaps	0	$ 0
Liabilities:
Interest rate swaps	0	$ 0
Recurring [Member] | Level III [Member] | Interest rate cap [Member]
Mortgage-backed securities:
Interest rate cap	0
Recurring [Member] | Level III [Member] | US Treasury Securities [Member]
Assets:
U.S. Treasury securities	$ 0