Recently Issued Accounting Pronouncements (Details) - USD ($) $ in Thousands	Jan. 01, 2019	Mar. 31, 2019		Dec. 31, 2018	Mar. 31, 2018	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease right-of-use assets	$ 28,923	$ 28,249		$ 0
Operating lease liabilities	30,853	30,187	[1]	0
Rent-related liabilities	2,900
Cumulative effect on retained earnings, tax	222
Cumulative effect on retained earnings, net of tax	722	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		$ (17,503)		$ (28,309)	$ (32,675)	$ (23,510)
Adjustments for Change in Accounting Principle [Domain]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Held to maturity debt securities, at amortized cost	10,415
Held to maturity debt securities, fair value	10,316
Unrealized losses on held to maturity securities, net of tax	$ (75)

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