Debt (Maturities of Long-term Debt) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013
Debt Disclosure [Abstract]
2014	$ 575,000
2015	105,000
2016	833,525	[1]
2017	140,000
2018	0
Thereafter	350,000
Total	$ 2,003,525

[1] Includes the balance outstanding as of December 31, 2013 of the $500 Million Unsecured Line of Credit. However, Piedmont may extend the term for up to one additional year (through two available six month extensions to a final extended maturity date of August 21, 2017) provided Piedmont is not then in default and upon payment of extension fees.