Fair Value of Financial Instruments - (Schedule of Fair Value of Financial Instruments) (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016	Jun. 30, 2016	Dec. 31, 2015
ASSETS:
Cash and cash equivalents	$ 129,827	$ 152,736	$ 147,939	$ 166,092
Investment securities available-for-sale (at fair value)	866,714	884,232
Mortgage-backed securities-residential mortgage pass-through securities issued or guaranteed by U.S. Government agencies or sponsored enterprises held-to-maturity	294,891	332,505
Non-marketable securities	18,468	14,949
Loans held-for-sale	7,067	24,187
LIABILITIES:
Time deposits	1,126,481	1,172,046
Securities sold under agreements to repurchase	119,213	92,011
Federal Home Loan Bank advances	129,115	38,665
Residential Mortgage Pass-Through Securities Issued or Guaranteed by U.S. Government Agencies or Sponsored Enterprises [Member]
ASSETS:
Investment securities available-for-sale (at fair value)	195,341	227,160
Mortgage-backed securities-residential mortgage pass-through securities issued or guaranteed by U.S. Government agencies or sponsored enterprises held-to-maturity	233,026	263,411
Other Residential MBS Issued or Guaranteed by U.S. Government Agencies or Sponsored Enterprises [Member]
ASSETS:
Investment securities available-for-sale (at fair value)	668,631	652,739
Mortgage-backed securities-residential mortgage pass-through securities issued or guaranteed by U.S. Government agencies or sponsored enterprises held-to-maturity	61,865	69,094
Other Securities [Member]
ASSETS:
Investment securities available-for-sale (at fair value)	419	419
Municipal [Member]
ASSETS:
Investment securities available-for-sale (at fair value)	2,323	3,914
Carrying Amount [Member] | Level 1 [Member]
ASSETS:
Cash and cash equivalents	129,827	152,736
Carrying Amount [Member] | Level 2 [Member]
ASSETS:
Non-marketable securities	18,468	14,949
Loans held-for-sale	7,067	24,187
Accrued interest receivable	13,294	12,562
LIABILITIES:
Deposit transaction accounts	2,730,976	2,696,603
Time deposits	1,126,481	1,172,046
Securities sold under agreements to repurchase	119,213	92,011
Federal Home Loan Bank advances	129,115	38,665
Accrued interest payable	5,098	4,973
Carrying Amount [Member] | Level 3 [Member]
ASSETS:
Loans receivable, net	3,087,945	2,860,921
Carrying Amount [Member] | Residential Mortgage Pass-Through Securities Issued or Guaranteed by U.S. Government Agencies or Sponsored Enterprises [Member] | Level 2 [Member]
ASSETS:
Investment securities available-for-sale (at fair value)	195,341	227,160
Mortgage-backed securities-residential mortgage pass-through securities issued or guaranteed by U.S. Government agencies or sponsored enterprises held-to-maturity	233,026	263,411
Carrying Amount [Member] | Other Residential MBS Issued or Guaranteed by U.S. Government Agencies or Sponsored Enterprises [Member] | Level 2 [Member]
ASSETS:
Investment securities available-for-sale (at fair value)	668,631	652,739
Mortgage-backed securities-residential mortgage pass-through securities issued or guaranteed by U.S. Government agencies or sponsored enterprises held-to-maturity	61,865	69,094
Carrying Amount [Member] | Other Securities [Member] | Level 3 [Member]
ASSETS:
Investment securities available-for-sale (at fair value)	419	419
Carrying Amount [Member] | Municipal [Member] | Level 2 [Member]
ASSETS:
Municipal obligations	2,058	3,648
Carrying Amount [Member] | Municipal [Member] | Level 3 [Member]
ASSETS:
Municipal obligations	265	265
Estimated Fair Value [Member] | Level 1 [Member]
ASSETS:
Cash and cash equivalents	129,827	152,736
Estimated Fair Value [Member] | Level 2 [Member]
ASSETS:
Non-marketable securities	18,468	14,949
Loans held-for-sale	7,067	24,187
Accrued interest receivable	13,294	12,562
LIABILITIES:
Deposit transaction accounts	2,730,976	2,696,603
Time deposits	1,126,481	1,172,046
Securities sold under agreements to repurchase	119,213	92,011
Federal Home Loan Bank advances	130,642	39,324
Accrued interest payable	5,098	4,973
Estimated Fair Value [Member] | Level 3 [Member]
ASSETS:
Loans receivable, net	3,096,298	2,879,860
Estimated Fair Value [Member] | Residential Mortgage Pass-Through Securities Issued or Guaranteed by U.S. Government Agencies or Sponsored Enterprises [Member] | Level 2 [Member]
ASSETS:
Investment securities available-for-sale (at fair value)	195,341	227,160
Mortgage-backed securities-residential mortgage pass-through securities issued or guaranteed by U.S. Government agencies or sponsored enterprises held-to-maturity	234,194	264,862
Estimated Fair Value [Member] | Other Residential MBS Issued or Guaranteed by U.S. Government Agencies or Sponsored Enterprises [Member] | Level 2 [Member]
ASSETS:
Investment securities available-for-sale (at fair value)	668,631	652,739
Mortgage-backed securities-residential mortgage pass-through securities issued or guaranteed by U.S. Government agencies or sponsored enterprises held-to-maturity	60,675	67,711
Estimated Fair Value [Member] | Other Securities [Member] | Level 3 [Member]
ASSETS:
Investment securities available-for-sale (at fair value)	419	419
Estimated Fair Value [Member] | Municipal [Member] | Level 2 [Member]
ASSETS:
Municipal obligations	2,058	3,648
Estimated Fair Value [Member] | Municipal [Member] | Level 3 [Member]
ASSETS:
Municipal obligations	265	265
Interest rate swap derivatives [Member] | Carrying Amount [Member] | Level 2 [Member]
ASSETS:
Derivative asset	10,694	11,428
LIABILITIES:
Derivative liability	4,729	3,279
Interest rate swap derivatives [Member] | Estimated Fair Value [Member] | Level 2 [Member]
ASSETS:
Derivative asset	10,694	11,428
LIABILITIES:
Derivative liability	4,729	3,279
Mortgage banking derivatives | Carrying Amount [Member] | Level 3 [Member]
ASSETS:
Derivative asset	157	287
LIABILITIES:
Derivative liability	26	187
Mortgage banking derivatives | Estimated Fair Value [Member] | Level 3 [Member]
ASSETS:
Derivative asset	157	287
LIABILITIES:
Derivative liability	$ 26	$ 187