Fair Value of Financial Instruments - (Schedule of Fair Value of Financial Instruments) (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016	Mar. 31, 2016	Dec. 31, 2015
ASSETS:
Cash and cash equivalents	$ 218,430	$ 152,736	$ 193,624	$ 166,092
Investment securities available-for-sale (at fair value)	921,881	884,232
Mortgage-backed securities-residential mortgage pass-through securities issued or guaranteed by U.S. Government agencies or sponsored enterprises held-to-maturity	313,446	332,505
Non-marketable securities	13,065	14,949
Loans held-for-sale	3,547	24,187
LIABILITIES:
Time deposits	1,184,994	1,172,046
Securities sold under agreements to repurchase	91,697	92,011
Federal Home Loan Bank advances	76,780	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)	210,034	227,160
Mortgage-backed securities-residential mortgage pass-through securities issued or guaranteed by U.S. Government agencies or sponsored enterprises held-to-maturity	247,775	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)	708,209	652,739
Mortgage-backed securities-residential mortgage pass-through securities issued or guaranteed by U.S. Government agencies or sponsored enterprises held-to-maturity	65,671	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)	3,219	3,914
Carrying Amount [Member] | Level 1 [Member]
ASSETS:
Cash and cash equivalents	218,430	152,736
Carrying Amount [Member] | Level 2 [Member]
ASSETS:
Non-marketable securities	13,065	14,949
Loans held-for-sale	3,547	24,187
Accrued interest receivable	14,332	12,562
LIABILITIES:
Deposit transaction accounts	2,782,949	2,696,603
Time deposits	1,184,994	1,172,046
Securities sold under agreements to repurchase	91,697	92,011
Federal Home Loan Bank advances	76,780	38,665
Accrued interest payable	6,246	4,973
Carrying Amount [Member] | Level 3 [Member]
ASSETS:
Loans receivable, net	2,953,655	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)	210,034	227,160
Mortgage-backed securities-residential mortgage pass-through securities issued or guaranteed by U.S. Government agencies or sponsored enterprises held-to-maturity	247,775	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)	708,209	652,739
Mortgage-backed securities-residential mortgage pass-through securities issued or guaranteed by U.S. Government agencies or sponsored enterprises held-to-maturity	65,671	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	2,954	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	218,430	152,736
Estimated Fair Value [Member] | Level 2 [Member]
ASSETS:
Non-marketable securities	13,065	14,949
Loans held-for-sale	3,547	24,187
Accrued interest receivable	14,332	12,562
LIABILITIES:
Deposit transaction accounts	2,782,949	2,696,603
Time deposits	1,184,994	1,172,046
Securities sold under agreements to repurchase	91,697	92,011
Federal Home Loan Bank advances	78,569	39,324
Accrued interest payable	6,246	4,973
Estimated Fair Value [Member] | Level 3 [Member]
ASSETS:
Loans receivable, net	2,960,288	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)	210,034	227,160
Mortgage-backed securities-residential mortgage pass-through securities issued or guaranteed by U.S. Government agencies or sponsored enterprises held-to-maturity	248,940	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)	708,209	652,739
Mortgage-backed securities-residential mortgage pass-through securities issued or guaranteed by U.S. Government agencies or sponsored enterprises held-to-maturity	64,330	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	2,954	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	12,580	11,428
LIABILITIES:
Derivative liability	3,401	3,279
Interest rate swap derivatives [Member] | Estimated Fair Value [Member] | Level 2 [Member]
ASSETS:
Derivative asset	12,580	11,428
LIABILITIES:
Derivative liability	3,401	3,279
Mortgage banking derivatives | Carrying Amount [Member] | Level 3 [Member]
ASSETS:
Derivative asset	283	287
LIABILITIES:
Derivative liability	75	187
Mortgage banking derivatives | Estimated Fair Value [Member] | Level 3 [Member]
ASSETS:
Derivative asset	283	287
LIABILITIES:
Derivative liability	$ 75	$ 187