Loans Receivable - Credit Quality Indicators (Details) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Financing Receivable, Recorded Investment [Line Items]
Pass	$ 2,393,307	$ 2,265,286
OAEM	32,418	44,098
Substandard	97,122	91,173
Doubtful	370	556
Total	2,523,217	2,401,113
Potential problem loans receivable	101,200	110,400
Government guaranteed potential problem loans	675	1,200
Commercial Business
Financing Receivable, Recorded Investment [Line Items]
Pass	1,863,418	1,807,190
OAEM	31,158	43,202
Substandard	80,560	72,373
Doubtful	370	556
Total	1,975,506	1,923,321
Commercial Business | Commercial and Industrial
Financing Receivable, Recorded Investment [Line Items]
Pass	585,387	563,002
OAEM	9,289	8,093
Substandard	29,410	25,333
Doubtful	114	298
Total	624,200	596,726
Commercial Business | Owner-occupied Commercial Real Estate
Financing Receivable, Recorded Investment [Line Items]
Pass	548,827	544,429
OAEM	5,279	11,662
Substandard	21,298	16,260
Doubtful	256	258
Total	575,660	572,609
Commercial Business | Non-owner Occupied Commercial Real Estate
Financing Receivable, Recorded Investment [Line Items]
Pass	729,204	699,759
OAEM	16,590	23,447
Substandard	29,852	30,780
Doubtful	0	0
Total	775,646	753,986
One-to-four Family Residential
Financing Receivable, Recorded Investment [Line Items]
Pass	76,204	71,457
OAEM	0	0
Substandard	1,070	1,091
Doubtful	0	0
Total	77,274	72,548
Real Estate Construction and Land Development
Financing Receivable, Recorded Investment [Line Items]
Pass	137,644	94,747
OAEM	1,260	896
Substandard	10,038	11,434
Doubtful	0	0
Total	148,942	107,077
Real Estate Construction and Land Development | One to Four Family Real Estate Construction
Financing Receivable, Recorded Investment [Line Items]
Pass	42,107	44,069
OAEM	1,260	896
Substandard	6,152	6,787
Doubtful	0	0
Total	49,519	51,752
Real Estate Construction and Land Development | Five or More Family Residential and Commercial Properties
Financing Receivable, Recorded Investment [Line Items]
Pass	95,537	50,678
OAEM	0	0
Substandard	3,886	4,647
Doubtful	0	0
Total	99,423	55,325
Consumer
Financing Receivable, Recorded Investment [Line Items]
Pass	316,041	291,892
OAEM	0	0
Substandard	5,454	6,275
Doubtful	0	0
Total	$ 321,495	$ 298,167