Long-term Debt - Corporate Office Lease (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2016 USD ($) option
Debt Instrument [Line Items]
Sale Leaseback Transaction, Net Book Value	$ 31,800
Lease term	20 years
Number of options to extend lease | option	4
Term of lease extension	5 years
Number of options to repurchase office building	2
Sale leaseback, annual rental payments	$ 3,300
Sale Leaseback, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
Minimum Lease Payments, Sale Leaseback Transactions, Next Twelve Months	3,367
Minimum Lease Payments, Sale Leaseback Transactions, within Two Years	3,409
Minimum Lease Payments, Sale Leaseback Transactions, within Three Years	3,451
Minimum Lease Payments, Sale Leaseback Transactions, within Four Years	3,494
Minimum Lease Payments, Sale Leaseback Transactions, within Five Years	$ 3,538
Option to Purchase at End of Year Five of Original Lease [Member]
Debt Instrument [Line Items]
Number of options to repurchase office building	1
Period elapsed on original lease, until option to repurchase building	5 years
Option to Purchase at End of Year Ten of Original Lease [Member]
Debt Instrument [Line Items]
Period elapsed on original lease, until option to repurchase building	10 years
Corporate Office Lease [Member]
Debt Instrument [Line Items]
Annual increase to lease payments (percent)	1.25%
Corporate Office Lease [Member] | Maximum [Member]
Debt Instrument [Line Items]
Annual increase to lease payments (percent)	2.00%