Accounting Pronouncements Recently Issued Narrative - Impact of implementation of new accounting standards (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Accounting Standards Update 2016-02 [Member]
Change in other assets due to adoption of new ASU	$ 49,200
Change in other liabilities due to adoption of new ASU	$ 48,200
Accounting Standards Update 2016-01 [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption			$ (46)
Retained Earnings [Member] | Accounting Standards Update 2016-02 [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption		$ 782
Retained Earnings [Member] | Accounting Standards Update 2016-01 [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption			$ (203)