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, 2017	Jun. 30, 2016	Dec. 31, 2016	Dec. 31, 2015
Cash and cash equivalents	$ 600,296,000	$ 453,939,000	$ 515,646,000	$ 443,420,000
Cash and Cash Equivalents, at Carrying Value	876,930,000	731,585,000	781,283,000	673,173,000
Restricted Cash and Cash Equivalents	276,634,000	277,646,000	265,637,000	229,753,000
Cash and Cash Equivalents inclusive of Restricted Cash [Member]
Cash and cash equivalents	$ 876,930,000	$ 731,585,000	$ 781,283,000	$ 673,173,000