Income Taxes (Narrative) (Details) - USD ($) $ in Thousands			3 Months Ended	12 Months Ended			15 Months Ended
		Jan. 01, 2018	Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2018
New Accounting Pronouncements Adopted and Recent Accounting Pronouncements [Line Items]
Reclassification of tax effects in AOCI resulting from the new federal corporate income tax rate	[1]	$ 0
Excess tax benefits related to stock compensation expense recognized in income tax expense				$ 5,089	$ 4,775
Excess tax benefits related to stock compensation expense recognized in additional paid-in capital						$ 1,055
Tax cuts and jobs act, change in tax rate, income tax expense (benefit)			$ 41,700	985			$ 42,700
Remeasurements of certain deferred tax assets and liabilities, net			33,100
Remeasurements of Tax credits and other tax benefits related to qualified affordable housing partnerships			7,900
Deferred tax benefits, net unrealized losses on available-for-sale securities recognized as other comprehensive income				3,600	1,500	16,400
Valuation allowance			256	128	256		128
Deferred tax assets, net			$ 97,406	117,641	97,406		117,641
Foreign pre-tax earnings				14,100	$ 7,300	$ 4,500
Undistributed earnings of foreign subsidiaries				52,300			52,300
Amount of unrecognized deferred tax liability				$ 6,200			$ 6,200
Retained Earnings
New Accounting Pronouncements Adopted and Recent Accounting Pronouncements [Line Items]
Reclassification of tax effects in AOCI resulting from the new federal corporate income tax rate	[1]	6,656
Retained Earnings | Accounting Standards Update 2018-02
New Accounting Pronouncements Adopted and Recent Accounting Pronouncements [Line Items]
Reclassification of tax effects in AOCI resulting from the new federal corporate income tax rate		6,656
AOCI, net of Tax
New Accounting Pronouncements Adopted and Recent Accounting Pronouncements [Line Items]
Reclassification of tax effects in AOCI resulting from the new federal corporate income tax rate	[1]	(6,656)
AOCI, net of Tax | Accounting Standards Update 2018-02
New Accounting Pronouncements Adopted and Recent Accounting Pronouncements [Line Items]
Reclassification of tax effects in AOCI resulting from the new federal corporate income tax rate		$ (6,656)

[1] Represents amounts reclassified from AOCI to retained earnings due to the early adoption of ASU 2018-02, Income Statement — Reporting Comprehensive Income (Topic 220): Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income in the first quarter of 2018. Refer to Note 1 — Summary of Significant Accounting Policies to the Consolidated Financial Statements for additional information.