Fair Value Measurements - Fair Value Measurement on Nonrecurring Basis (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Level 1
Fair value measurements of assets on a nonrecurring basis
Fair Value	$ 0		$ 0		$ 0
Level 2
Fair value measurements of assets on a nonrecurring basis
Fair Value	0		0		0
Level 3
Fair value measurements of assets on a nonrecurring basis
Fair Value	2,725,031		2,725,031		2,675,811
Nonrecurring | Owner-occupied Commercial Real Estate
Fair value measurements of assets on a nonrecurring basis
Net Losses (Gains) Recorded in Earnings			8
Nonrecurring | Commercial Business | Owner-occupied Commercial Real Estate
Fair value measurements of assets on a nonrecurring basis
Fair Value	179		179
Net Losses (Gains) Recorded in Earnings	3
Nonrecurring | Commercial Business | Owner-occupied Commercial Real Estate | Level 1
Fair value measurements of assets on a nonrecurring basis
Fair Value	0		0
Nonrecurring | Commercial Business | Owner-occupied Commercial Real Estate | Level 2
Fair value measurements of assets on a nonrecurring basis
Fair Value	0		0
Nonrecurring | Commercial Business | Owner-occupied Commercial Real Estate | Level 3
Fair value measurements of assets on a nonrecurring basis
Fair Value	179		179
Nonrecurring | Impaired Loans
Fair value measurements of assets on a nonrecurring basis
Basis	372		372		1,829
Fair Value	359		359		1,634
Net Losses (Gains) Recorded in Earnings	3	$ 54	12	$ 47
Nonrecurring | Impaired Loans | Level 1
Fair value measurements of assets on a nonrecurring basis
Fair Value	0		0		0
Nonrecurring | Impaired Loans | Level 2
Fair value measurements of assets on a nonrecurring basis
Fair Value	0		0		0
Nonrecurring | Impaired Loans | Level 3
Fair value measurements of assets on a nonrecurring basis
Fair Value	359		359		1,634
Nonrecurring | Impaired Loans | Commercial Business
Fair value measurements of assets on a nonrecurring basis
Basis	354		354		985
Fair Value	343		343		803
Net Losses (Gains) Recorded in Earnings	3	60	15	60
Nonrecurring | Impaired Loans | Commercial Business | Level 1
Fair value measurements of assets on a nonrecurring basis
Fair Value	0		0		0
Nonrecurring | Impaired Loans | Commercial Business | Level 2
Fair value measurements of assets on a nonrecurring basis
Fair Value	0		0		0
Nonrecurring | Impaired Loans | Commercial Business | Level 3
Fair value measurements of assets on a nonrecurring basis
Fair Value	343		343		803
Nonrecurring | Impaired Loans | Commercial Business | Commercial and Industrial
Fair value measurements of assets on a nonrecurring basis
Basis	172		172		205
Fair Value	164		164		200
Net Losses (Gains) Recorded in Earnings	0	60	7	60
Nonrecurring | Impaired Loans | Commercial Business | Commercial and Industrial | Level 1
Fair value measurements of assets on a nonrecurring basis
Fair Value	0		0		0
Nonrecurring | Impaired Loans | Commercial Business | Commercial and Industrial | Level 2
Fair value measurements of assets on a nonrecurring basis
Fair Value	0		0		0
Nonrecurring | Impaired Loans | Commercial Business | Commercial and Industrial | Level 3
Fair value measurements of assets on a nonrecurring basis
Fair Value	164		164		200
Nonrecurring | Impaired Loans | Commercial Business | Owner-occupied Commercial Real Estate
Fair value measurements of assets on a nonrecurring basis
Basis	182		182		780
Fair Value					603
Net Losses (Gains) Recorded in Earnings		0		0
Nonrecurring | Impaired Loans | Commercial Business | Owner-occupied Commercial Real Estate | Level 1
Fair value measurements of assets on a nonrecurring basis
Fair Value					0
Nonrecurring | Impaired Loans | Commercial Business | Owner-occupied Commercial Real Estate | Level 2
Fair value measurements of assets on a nonrecurring basis
Fair Value					0
Nonrecurring | Impaired Loans | Commercial Business | Owner-occupied Commercial Real Estate | Level 3
Fair value measurements of assets on a nonrecurring basis
Fair Value					603
Nonrecurring | Impaired Loans | Real Estate Construction and Land Development
Fair value measurements of assets on a nonrecurring basis
Basis					828
Fair Value					822
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
Fair Value					0
Nonrecurring | Impaired Loans | Real Estate Construction and Land Development | Level 2
Fair value measurements of assets on a nonrecurring basis
Fair Value					0
Nonrecurring | Impaired Loans | Real Estate Construction and Land Development | Level 3
Fair value measurements of assets on a nonrecurring basis
Fair Value					822
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
Basis					828
Fair Value					822
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
Fair Value					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
Fair Value					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
Fair Value					822
Nonrecurring | Impaired Loans | Consumer
Fair value measurements of assets on a nonrecurring basis
Basis	18		18		16
Fair Value	16		16		9
Net Losses (Gains) Recorded in Earnings	0	$ 0	(3)	$ 0
Nonrecurring | Impaired Loans | Consumer | Level 1
Fair value measurements of assets on a nonrecurring basis
Fair Value	0		0		0
Nonrecurring | Impaired Loans | Consumer | Level 2
Fair value measurements of assets on a nonrecurring basis
Fair Value	0		0		0
Nonrecurring | Impaired Loans | Consumer | Level 3
Fair value measurements of assets on a nonrecurring basis
Fair Value	$ 16		$ 16		$ 9