Fair Value Measurements - Fair Value Measurement on Nonrecurring Basis (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
Level 1
Fair value measurements of assets on a nonrecurring basis
Impaired originated loans, Total	$ 0		$ 0		$ 0
Level 2
Fair value measurements of assets on a nonrecurring basis
Impaired originated loans, Total	0		0		0
Level 3
Fair value measurements of assets on a nonrecurring basis
Impaired originated loans, Total	2,559,931		2,559,931		2,441,531
Nonrecurring
Fair value measurements of assets on a nonrecurring basis
Total, Basis	1,861		1,861		1,753
Total assets measured	1,524		1,524		1,719
Total, Net Losses (Gains) Recorded in Earnings	125	$ (2)	307	$ 127
Nonrecurring | Level 1
Fair value measurements of assets on a nonrecurring basis
Total assets measured	0		0		0
Nonrecurring | Level 2
Fair value measurements of assets on a nonrecurring basis
Total assets measured	0		0		0
Nonrecurring | Level 3
Fair value measurements of assets on a nonrecurring basis
Total assets measured	1,524		1,524		1,719
Nonrecurring | Other Real Estate Owned
Fair value measurements of assets on a nonrecurring basis
Total, Basis	868		868
Other real estate owned	608		608
Total, Net Losses (Gains) Recorded in Earnings	71		260
Nonrecurring | Other Real Estate Owned | Level 1
Fair value measurements of assets on a nonrecurring basis
Other real estate owned	0		0
Nonrecurring | Other Real Estate Owned | Level 2
Fair value measurements of assets on a nonrecurring basis
Other real estate owned	0		0
Nonrecurring | Other Real Estate Owned | Level 3
Fair value measurements of assets on a nonrecurring basis
Other real estate owned	608		608
Nonrecurring | Impaired Loans
Fair value measurements of assets on a nonrecurring basis
Total, Basis	993		993
Impaired originated loans, Total	916		916
Total, Net Losses (Gains) Recorded in Earnings	54		47
Nonrecurring | Impaired Loans | Level 1
Fair value measurements of assets on a nonrecurring basis
Impaired originated loans, Total	0		0
Nonrecurring | Impaired Loans | Level 2
Fair value measurements of assets on a nonrecurring basis
Impaired originated loans, Total	0		0
Nonrecurring | Impaired Loans | Level 3
Fair value measurements of assets on a nonrecurring basis
Impaired originated loans, Total	916		916		$ 1,719
Nonrecurring | Impaired Loans | Commercial Business
Fair value measurements of assets on a nonrecurring basis
Total, Basis	114		114
Impaired originated loans, Total	54		54
Total, Net Losses (Gains) Recorded in Earnings	60		60
Nonrecurring | Impaired Loans | Commercial Business | Level 1
Fair value measurements of assets on a nonrecurring basis
Impaired originated loans, Total	0		0
Nonrecurring | Impaired Loans | Commercial Business | Level 2
Fair value measurements of assets on a nonrecurring basis
Impaired originated loans, Total	0		0
Nonrecurring | Impaired Loans | Commercial Business | Level 3
Fair value measurements of assets on a nonrecurring basis
Impaired originated loans, Total	54		54
Nonrecurring | Impaired Loans | Commercial Business | Commercial and Industrial
Fair value measurements of assets on a nonrecurring basis
Total, Basis	114		114
Impaired originated loans, Total	54		54
Total, Net Losses (Gains) Recorded in Earnings	60		60
Nonrecurring | Impaired Loans | Commercial Business | Commercial and Industrial | Level 1
Fair value measurements of assets on a nonrecurring basis
Impaired originated loans, Total	0		0
Nonrecurring | Impaired Loans | Commercial Business | Commercial and Industrial | Level 2
Fair value measurements of assets on a nonrecurring basis
Impaired originated loans, Total	0		0
Nonrecurring | Impaired Loans | Commercial Business | Commercial and Industrial | Level 3
Fair value measurements of assets on a nonrecurring basis
Impaired originated loans, Total	54		54
Nonrecurring | Impaired Loans | Real Estate Construction and Land Development
Fair value measurements of assets on a nonrecurring basis
Total, Basis	879		879
Impaired originated loans, Total	862		862
Total, Net Losses (Gains) Recorded in Earnings	(6)		(13)
Nonrecurring | Impaired Loans | Real Estate Construction and Land Development | Level 1
Fair value measurements of assets on a nonrecurring basis
Impaired originated loans, Total	0		0
Nonrecurring | Impaired Loans | Real Estate Construction and Land Development | Level 2
Fair value measurements of assets on a nonrecurring basis
Impaired originated loans, Total	0		0
Nonrecurring | Impaired Loans | Real Estate Construction and Land Development | Level 3
Fair value measurements of assets on a nonrecurring basis
Impaired originated loans, Total	862		862
Nonrecurring | Impaired Loans | Real Estate Construction and Land Development | One to Four Family Real Estate Construction
Fair value measurements of assets on a nonrecurring basis
Total, Basis	879		879
Impaired originated loans, Total	862		862
Total, Net Losses (Gains) Recorded in Earnings	(6)		(13)
Nonrecurring | Impaired Loans | Real Estate Construction and Land Development | One to Four Family Real Estate Construction | Level 1
Fair value measurements of assets on a nonrecurring basis
Impaired originated loans, Total	0		0
Nonrecurring | Impaired Loans | Real Estate Construction and Land Development | One to Four Family Real Estate Construction | Level 2
Fair value measurements of assets on a nonrecurring basis
Impaired originated loans, Total	0		0
Nonrecurring | Impaired Loans | Real Estate Construction and Land Development | One to Four Family Real Estate Construction | Level 3
Fair value measurements of assets on a nonrecurring basis
Impaired originated loans, Total	$ 862		$ 862