Recently Issued Accounting Pronouncements (Details) - USD ($) $ in Thousands	Jan. 01, 2019	Jun. 30, 2019		Mar. 31, 2019	Dec. 31, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease right-of-use assets	$ 28,900	$ 28,174			$ 0
Operating lease liabilities	30,900	30,210	[1]		0
Rent-related liabilities	2,900
Cumulative effect on retained earnings, tax	222
Cumulative effect on retained earnings, net of tax	722
Held to maturity debt securities, at amortized cost		0			10,415
Held to maturity debt securities, fair value		0			10,316
Unrealized losses on held to maturity securities, net of tax		$ (11,866)		$ (17,503)	$ (28,309)	$ (35,062)	$ (32,675)	$ (23,510)
Retained Earnings [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect on retained earnings, net of tax	$ 722

[1] Includes short-term operating lease liabilities of $2.5 million.