Debt Obligations, net (Schedule of Debt) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2015		Dec. 31, 2014
Debt Instrument [Line Items]
Total debt obligations	$ 4,271,867		$ 4,034,349
Debt discounts, net	(10,339)		(11,665)
Total debt obligations, net	4,261,528		4,022,684
2012 Tranche A-2 Facility
Debt Instrument [Line Items]
Total debt obligations	348,185	[1]	358,504	[1]
Stated Interest Rates	7.00%
Variable interest rate, spread	5.75%	[1]
Variable interest rate, basis	LIBOR	[1]
2015 Revolving Credit Facility
Debt Instrument [Line Items]
Total debt obligations	250,000	[2]	0	[2]
Term loans collateralized by net lease assets
Debt Instrument [Line Items]
Total debt obligations	246,792	[3]	248,955	[3]
Weighted average interest rate	5.30%
Stated interest rate, minimum	4.851%	[3]
Stated interest rate, maximum	7.26%	[3]
Total secured credit facilities and term loans
Debt Instrument [Line Items]
Total debt obligations	844,977		607,459
6.05% senior notes
Debt Instrument [Line Items]
Total debt obligations	105,765		105,765
Stated Interest Rates	6.05%
5.875% senior notes
Debt Instrument [Line Items]
Total debt obligations	261,403		261,403
Stated Interest Rates	5.875%
3.875% senior notes
Debt Instrument [Line Items]
Total debt obligations	265,000		265,000
Stated Interest Rates	3.875%
3.0% senior convertible notes
Debt Instrument [Line Items]
Total debt obligations	200,000	[4]	200,000	[4]
Stated Interest Rates	3.00%	[4]
Convertible debt conversion ratio	0.085
Convertible debt conversion price	$ 11.77
1.50% senior convertible notes
Debt Instrument [Line Items]
Total debt obligations	200,000	[5]	200,000	[5]
Stated Interest Rates	1.50%	[5]
Convertible debt conversion ratio	0.0578
Convertible debt conversion price	$ 17.29
5.85% senior notes
Debt Instrument [Line Items]
Total debt obligations	99,722		99,722
Stated Interest Rates	5.85%
9.0% senior notes
Debt Instrument [Line Items]
Total debt obligations	275,000		275,000
Stated Interest Rates	9.00%
4.00% senior notes
Debt Instrument [Line Items]
Total debt obligations	550,000		550,000
Stated Interest Rates	4.00%
7.125% senior notes
Debt Instrument [Line Items]
Total debt obligations	300,000		300,000
Stated Interest Rates	7.125%
4.875% senior notes
Debt Instrument [Line Items]
Total debt obligations	300,000		300,000
Stated Interest Rates	4.875%
5.00% senior notes
Debt Instrument [Line Items]
Total debt obligations	770,000		770,000
Stated Interest Rates	5.00%
Unsecured Notes
Debt Instrument [Line Items]
Total debt obligations	3,326,890		3,326,890
Other debt obligations
Debt Instrument [Line Items]
Total debt obligations	$ 100,000		$ 100,000
Variable interest rate, spread	1.50%
Variable interest rate, basis	LIBOR
Minimum | 2012 Tranche A-2 Facility
Debt Instrument [Line Items]
Variable interest rate, spread	1.25%
Property One | London Interbank Offered Rate (LIBOR) | Term loans collateralized by net lease assets
Debt Instrument [Line Items]
Variable interest rate, spread	2.00%
Base Rate [Member] | London Interbank Offered Rate (LIBOR) | 2015 Revolving Credit Facility
Debt Instrument [Line Items]
Variable interest rate, spread	1.00%
Base Rate [Member] | Federal Funds Effective Swap Rate [Member] | 2015 Revolving Credit Facility
Debt Instrument [Line Items]
Variable interest rate, spread	0.50%
Base Rate [Member] | Minimum | 2015 Revolving Credit Facility
Debt Instrument [Line Items]
Debt instrument, margin	1.25%
Base Rate [Member] | Maximum [Member] | 2015 Revolving Credit Facility
Debt Instrument [Line Items]
Debt instrument, margin	1.75%
London Interbank Offered Rate (LIBOR) | Minimum | 2015 Revolving Credit Facility
Debt Instrument [Line Items]
Debt instrument, margin	2.25%
London Interbank Offered Rate (LIBOR) | Maximum [Member] | 2015 Revolving Credit Facility
Debt Instrument [Line Items]
Debt instrument, margin	2.75%

[1] The loan has a LIBOR floor of 1.25%. As of March 31, 2015, inclusive of the floor, the 2012 Tranche A-2 Facility loan incurred interest at a rate of 7.00%.

[2] The loan bears interest at the Company's election of either (i) a base rate, which is the greater of (a) prime, (b) federal funds plus 0.5% or (c) LIBOR plus 1.00% and subject to a margin ranging from 1.25% to 1.75%, or (ii) LIBOR subject to a margin ranging from 2.25% to 2.75%. At maturity, the Company may convert outstanding borrowings to a one year term loan which matures in quarterly installments through March 2019.

[3] As of March 31, 2015 and December 31, 2014, includes a loan with a floating rate of LIBOR plus 2.00%. As of March 31, 2015, the weighted average interest rate of these loans is 5.3%.

[4] The Company's 3.0% senior convertible fixed rate notes due November 2016 ("3.0% Convertible Notes") are convertible at the option of the holders, into 85.0 shares per $1,000 principal amount of 3.0% Convertible Notes, at $11.77 per share at any time prior to the close of business on November 14, 2016.

[5] The Company's 1.50% senior convertible fixed rate notes due November 2016 ("1.50% Convertible Notes") are convertible at the option of the holders, into 57.8 shares per $1,000 principal amount of 1.50% Convertible Notes, at $17.29 per share at any time prior to the close of business on November 14, 2016.