Debt Securities Available for Sale - Securities Available-for-Sale (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 1,095,282	$ 1,049,932
Gross Unrealized Gains	6,583	2,994
Gross Unrealized (Losses)	(11,688)	(20,058)
Debt securities available for sale, at fair value	1,090,177	1,032,868
U.S. government and agency obligations
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	54,621	54,821
Gross Unrealized Gains	240	53
Gross Unrealized (Losses)	(344)	(717)
Debt securities available for sale, at fair value	54,517	54,157
Mortgage-backed securities and collateralized mortgage obligations
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	970,978	934,631
Gross Unrealized Gains	6,240	2,812
Gross Unrealized (Losses)	(10,089)	(17,436)
Debt securities available for sale, at fair value	967,129	920,007
Municipal obligations
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	190	987
Gross Unrealized Gains	0	0
Gross Unrealized (Losses)	0	0
Debt securities available for sale, at fair value	190	987
Corporate debt securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	64,493	54,493
Gross Unrealized Gains	103	129
Gross Unrealized (Losses)	(792)	(1,155)
Debt securities available for sale, at fair value	63,804	53,467
Trust preferred securities
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	5,000	5,000
Gross Unrealized Gains	0	0
Gross Unrealized (Losses)	(463)	(750)
Debt securities available for sale, at fair value	$ 4,537	$ 4,250

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (b)
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Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

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Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

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-Publisher FASB
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-Section 50
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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
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