Supplemental Disclosures of Cash Flow Information and Non-Cash Financing and Investing Activities Restricted Cash (Details) - USD ($)	6 Months Ended		12 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018	Dec. 31, 2017
Cash and cash equivalents	$ 432,548,000	$ 477,928,000	$ 438,961,000	$ 573,383,000
Cash and Cash Equivalents, at Carrying Value	814,781,000	787,159,000	777,596,000	824,088,000
Restricted Cash and Cash Equivalents	382,233,000	309,231,000	338,635,000	250,705,000
Cash and Cash Equivalents inclusive of Restricted Cash [Member]
Cash and Cash Equivalents, Period Increase (Decrease)	37,185,000	(36,929,000)
Cash and cash equivalents	$ 814,781,000	$ 787,159,000	$ 777,596,000	$ 824,088,000