Operating Leases (Narrative) (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2020 USD ($)
Lessee Lease Description [Line Items]
Operating lease right-of-use assets	$ 668,700
Operating lease liabilities	$ 708,502
Minimum [Member] | Office Space and Office Equipment [Member]
Lessee Lease Description [Line Items]
Operating leases remaining lease term	1 year
Maximum [Member] | Office Space and Office Equipment [Member]
Lessee Lease Description [Line Items]
Operating leases remaining lease term	15 years